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Wang YL, Lin HC, Liang T, Lin JCY, Simmer JP, Hu JCC, Wang SK. ENAM Mutations Can Cause Hypomaturation Amelogenesis Imperfecta. J Dent Res 2024:220345241236695. [PMID: 38716742 DOI: 10.1177/00220345241236695] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/12/2024] Open
Abstract
Amelogenesis imperfecta (AI) is a diverse group of inherited diseases featured by various presentations of enamel malformations that are caused by disturbances at different stages of enamel formation. While hypoplastic AI suggests a thickness defect of enamel resulting from aberrations during the secretory stage of amelogenesis, hypomaturation AI indicates a deficiency of enamel mineralization and hardness established at the maturation stage. Mutations in ENAM, which encodes the largest enamel matrix protein, enamelin, have been demonstrated to cause generalized or local hypoplastic AI. Here, we characterized 2 AI families with disparate hypoplastic and hypomaturation enamel defects and identified 2 distinct indel mutations at the same location of ENAM, c588+1del and c.588+1dup. Minigene splicing assays demonstrated that they caused frameshifts and truncation of ENAM proteins, p.Asn197Ilefs*81 and p.Asn197Glufs*25, respectively. In situ hybridization of Enam on mouse mandibular incisors confirmed its restricted expression in secretory stage ameloblasts and suggested an indirect pathogenic mechanism underlying hypomaturation AI. In silico analyses indicated that these 2 truncated ENAMs might form amyloid structures and cause protein aggregation with themselves and with wild-type protein through the added aberrant region at their C-termini. Consistently, protein secretion assays demonstrated that the truncated proteins cannot be properly secreted and impede secretion of wild-type ENAM. Moreover, compared to the wild-type, overexpression of the mutant proteins significantly increased endoplasmic reticulum stress and upregulated the expression of unfolded protein response (UPR)-related genes and TNFRSF10B, a UPR-controlled proapoptotic gene. Caspase, terminal deoxynucleotidyl transferase UTP nick-end labeling (TUNEL), and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assays further revealed that both truncated proteins, especially p.Asn197Ilefs*81, induced cell apoptosis and decreased cell survival, suggesting that the 2 ENAM mutations cause AI through ameloblast cell pathology and death rather than through a simple loss of function. This study demonstrates that an ENAM mutation can lead to generalized hypomaturation enamel defects and suggests proteinopathy as a potential pathogenesis for ENAM-associated AI.
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Affiliation(s)
- Y-L Wang
- Department of Dentistry, National Taiwan University School of Dentistry, Taipei City, Taiwan
- Department of Pediatric Dentistry, National Taiwan University Children's Hospital, Taipei City, Taiwan
| | - H-C Lin
- Department of Dentistry, National Taiwan University School of Dentistry, Taipei City, Taiwan
| | - T Liang
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, USA
| | - J C-Y Lin
- Department of Orthodontics and Pediatric Dentistry, School of Dentistry, National Defense Medical University, Taipei City, Taiwan
| | - J P Simmer
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, USA
| | - J C-C Hu
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, USA
| | - S-K Wang
- Department of Dentistry, National Taiwan University School of Dentistry, Taipei City, Taiwan
- Department of Pediatric Dentistry, National Taiwan University Children's Hospital, Taipei City, Taiwan
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Wang SK, Zhang H, Wang YL, Seymen F, Koruyucu M, Simmer JP, Hu JCC. Phenotypic variability in LAMA3-associated amelogenesis imperfecta. Oral Dis 2023; 29:3514-3524. [PMID: 36326426 PMCID: PMC10154430 DOI: 10.1111/odi.14425] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Revised: 08/04/2022] [Accepted: 10/26/2022] [Indexed: 11/06/2022]
Abstract
OBJECTIVE Amelogenesis imperfecta (AI) is defined as inherited enamel malformations. LAMA3 (laminin alpha-3) encodes a critical protein component of the basement membrane (laminin-332). Individuals carrying heterozygous LAMA3 mutations have previously been shown to have localized enamel defects. This study aimed to define clinical phenotypes and to discern the genetic etiology for four AI kindreds. MATERIALS AND METHODS Whole-exome analyses were conducted to search for sequence variants associated with the disorder, and micro-computed tomography (μCT) to characterize the enamel defects. RESULTS The predominant enamel phenotype was generalized thin enamel with defective pits and grooves. Horizonal bands of hypoplastic enamel with chalky-white discoloration and enamel hypomineralization were also observed and demonstrated by μCT analyses of affected teeth. Four disease-causing LAMA3 mutations (NM_198129.4:c.3712dup; c.5891dup; c.7367del; c.9400G > C) were identified. Compound heterozygous MMP20 mutations (NM_004771.4:c.539A > G; c.692C > T) were also found in one proband with more severe enamel defects, suggesting a mutational synergism on disease phenotypes. Further analyses of the AI-causing mutations suggested that both α3A (short) and α3B (long) isoforms of LAMA3 are essential for enamel formation. CONCLUSIONS Heterozygous LAMA3 mutations can cause generalized enamel defects (AI1A) with variable expressivity. Laminin-332 is critical not only for appositional growth but also enamel maturation.
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Affiliation(s)
- Shih-Kai Wang
- Department of Dentistry, National Taiwan University School of Dentistry, No.1, Changde St., Taipei City 100, Taiwan
- Department of Pediatric Dentistry, National Taiwan University Children’s Hospital, No.8, Zhongshan S. Rd., Taipei City 100, Taiwan
| | - Hong Zhang
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1011 North University, Ann Arbor, MI 48108, USA
| | - Yin-Lin Wang
- Department of Dentistry, National Taiwan University School of Dentistry, No.1, Changde St., Taipei City 100, Taiwan
- Department of Pediatric Dentistry, National Taiwan University Children’s Hospital, No.8, Zhongshan S. Rd., Taipei City 100, Taiwan
| | - Figen Seymen
- Department of Pedodontics, Faculty of Dentistry, Altinbas University, Istanbul, 34147, Turkey
| | - Mine Koruyucu
- Department of Pedodontics, Faculty of Dentistry, Istanbul University, Istanbul, 34116, Turkey
| | - James P. Simmer
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1011 North University, Ann Arbor, MI 48108, USA
| | - Jan C.-C. Hu
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1011 North University, Ann Arbor, MI 48108, USA
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Wang SK, Zhang H, Wang YL, Lin HY, Seymen F, Koruyucu M, Wright JT, Kim JW, Simmer JP, Hu JCC. FAM20A mutations and transcriptome analyses of dental pulp tissues of enamel renal syndrome. Int Endod J 2023; 56:943-954. [PMID: 37159186 PMCID: PMC10524697 DOI: 10.1111/iej.13928] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2023] [Revised: 05/01/2023] [Accepted: 05/02/2023] [Indexed: 05/10/2023]
Abstract
AIM Biallelic loss-of-function FAM20A mutations cause amelogenesis imperfecta (AI) type IG, better known as enamel renal syndrome (ERS), characterized by severe enamel hypoplasia, delayed/failed tooth eruption, intrapulpal calcifications, gingival hyperplasia and nephrocalcinosis. FAM20A binds to FAM20C, the Golgi casein kinase (GCK) and potentiates its function to phosphorylate secreted proteins critical for biomineralization. While many FAM20A pathogenic mutations have been reported, the pathogeneses of orodental anomalies in ERS remain to be elucidated. This study aimed to identify disease-causing mutations for patients with ERS phenotypes and to discern the molecular mechanism underlying ERS intrapulpal calcifications. METHODOLOGY Phenotypic characterization and whole exome analyses were conducted for 8 families and 2 sporadic cases with hypoplastic AI. A minigene assay was performed to investigate the molecular consequences of a FAM20A splice-site variant. RNA sequencing followed by transcription profiling and gene ontology (GO) analyses were carried out for dental pulp tissues of ERS and the control. RESULTS Biallelic FAM20A mutations were demonstrated for each affected individual, including 7 novel pathogenic variants: c.590-5T>A, c.625T>A (p.Cys209Ser), c.771del (p.Gln258Argfs*28), c.832_835delinsTGTCCGACGGTGTCCGACGGTGTC CA (p.Val278Cysfs*29), c.1232G>A (p.Arg411Gln), c.1297A>G (p.Arg433Gly) and c.1351del (p.Gln451Serfs*4). The c.590-5T>A splice-site mutation caused Exon 3 skipping, which resulted in an in-frame deletion of a unique region of the FAM20A protein, p.(Asp197_Ile214delinsVal). Analyses of differentially expressed genes in ERS pulp tissues demonstrated that genes involved in biomineralization, particularly dentinogenesis, were significantly upregulated, such as DSPP, MMP9, MMP20 and WNT10A. Enrichment analyses indicated overrepresentation of gene sets associated with BMP and SMAD signalling pathways. In contrast, GO terms related to inflammation and axon development were underrepresented. Among BMP signalling genes, BMP agonists GDF7, GDF15, BMP3, BMP8A, BMP8B, BMP4 and BMP6 were upregulated, while BMP antagonists GREM1, BMPER and VWC2 showed decreased expression in ERS dental pulp tissues. CONCLUSIONS Upregulation of BMP signalling underlies intrapulpal calcifications in ERS. FAM20A plays an essential role in pulp tissue homeostasis and prevention of ectopic mineralization in soft tissues. This critical function probably depends upon MGP (matrix Gla protein), a potent mineralization inhibitor that must be properly phosphorylated by FAM20A-FAM20C kinase complex.
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Affiliation(s)
- Shih-Kai Wang
- Department of Dentistry, National Taiwan University School of Dentistry, No.1, Changde St., Taipei City 100229, Taiwan
- Department of Pediatric Dentistry, National Taiwan University Children’s Hospital, No.8, Zhongshan S. Rd., Taipei City 100226, Taiwan
| | - Hong Zhang
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1011 North University Ave., Ann Arbor, MI 48108, USA
| | - Yin-Lin Wang
- Department of Dentistry, National Taiwan University School of Dentistry, No.1, Changde St., Taipei City 100229, Taiwan
- Department of Pediatric Dentistry, National Taiwan University Children’s Hospital, No.8, Zhongshan S. Rd., Taipei City 100226, Taiwan
| | - Hung-Ying Lin
- Department of Oral and Maxillofacial Surgery, National Taiwan University Hospital; No.1, Changde St., Taipei City 100229, Taiwan
| | - Figen Seymen
- Department of Pedodontics, Faculty of Dentistry, Altinbas University, Istanbul, 34147, Turkey
| | - Mine Koruyucu
- Department of Pedodontics, Faculty of Dentistry, Istanbul University, Istanbul, 34116, Turkey
| | - J Timothy Wright
- Department of Pediatric Dentistry, University of North Carolina School of Dentistry, CB 7450, 228 Brauer Hall, Chapel Hill, NC 27599, USA
| | - Jung-Wook Kim
- Department of Molecular Genetics & Dental Research Institute, School of Dentistry, Seoul National University, Seoul 03080, Republic of Korea
- Department of Pediatric Dentistry & Dental Research Institute, School of Dentistry, Seoul National University, Seoul 03080, Republic of Korea
| | - James P. Simmer
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1011 North University Ave., Ann Arbor, MI 48108, USA
| | - Jan C.-C. Hu
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1011 North University Ave., Ann Arbor, MI 48108, USA
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Hsu YH, Hassan A, Trout A, Bartlett JD, Smith CE, Simmer JP, McComb DW. The Characterization of Hydroxyapatite and Octa-calcium Phosphate with Electron Energy Loss Spectroscopy. Microsc Microanal 2023; 29:1223-1225. [PMID: 37613591 DOI: 10.1093/micmic/ozad067.629] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/25/2023]
Affiliation(s)
- Ya-Hsiang Hsu
- Department of Materials Science and Engineering, The Ohio State University, Columbus, OH, USA
| | - Asra Hassan
- Center for Electron Microscopy and Analysis, The Ohio State University, Columbus, OH, USA
- Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson AFB, OH, USA
| | - Amanda Trout
- Center for Electron Microscopy and Analysis, The Ohio State University, Columbus, OH, USA
| | - John D Bartlett
- Division of Biosciences, Ohio State University College of Dentistry, Columbus, OH, USA
| | - Charles E Smith
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, USA
- Department of Anatomy and Cell Biology, Faculty of Medicine and Health Sciences, McGill University, Montreal, QC, Canada
| | - James P Simmer
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, USA
| | - David W McComb
- Department of Materials Science and Engineering, The Ohio State University, Columbus, OH, USA
- Center for Electron Microscopy and Analysis, The Ohio State University, Columbus, OH, USA
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Liang T, Smith CE, Hu Y, Zhang H, Zhang C, Xu Q, Lu Y, Qi L, Hu JCC, Simmer JP. Dentin defects caused by a Dspp -1 frameshift mutation are associated with the activation of autophagy. Sci Rep 2023; 13:6393. [PMID: 37076504 PMCID: PMC10115861 DOI: 10.1038/s41598-023-33362-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2023] [Accepted: 04/12/2023] [Indexed: 04/21/2023] Open
Abstract
Dentin sialophosphoprotein (DSPP) is primarily expressed by differentiated odontoblasts (dentin-forming cells), and transiently expressed by presecretory ameloblasts (enamel-forming cells). Disease-causing DSPP mutations predominantly fall into two categories: 5' mutations affecting targeting and trafficking, and 3' - 1 frameshift mutations converting the repetitive, hydrophilic, acidic C-terminal domain into a hydrophobic one. We characterized the dental phenotypes and investigated the pathological mechanisms of DsppP19L and Dspp-1fs mice that replicate the two categories of human DSPP mutations. In DsppP19L mice, dentin is less mineralized but contains dentinal tubules. Enamel mineral density is reduced. Intracellular accumulation and ER retention of DSPP is observed in odontoblasts and ameloblasts. In Dspp-1fs mice, a thin layer of reparative dentin lacking dentinal tubules is deposited. Odontoblasts show severe pathosis, including intracellular accumulation and ER retention of DSPP, strong ubiquitin and autophagy activity, ER-phagy, and sporadic apoptosis. Ultrastructurally, odontoblasts show extensive autophagic vacuoles, some of which contain fragmented ER. Enamel formation is comparable to wild type. These findings distinguish molecular mechanisms underlying the dental phenotypes of DsppP19L and Dspp-1fs mice and support the recently revised Shields classification of dentinogenesis imperfecta caused by DSPP mutations in humans. The Dspp-1fs mice may be valuable for the study of autophagy and ER-phagy.
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Affiliation(s)
- Tian Liang
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1011 North University, Ann Arbor, MI, 48109-1078, USA.
| | - Charles E Smith
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1011 North University, Ann Arbor, MI, 48109-1078, USA
- Department of Anatomy & Cell Biology, Faculty of Medicine & Health Sciences, McGill University, Montreal, QC, Canada
| | - Yuanyuan Hu
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1011 North University, Ann Arbor, MI, 48109-1078, USA
| | - Hong Zhang
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1011 North University, Ann Arbor, MI, 48109-1078, USA
| | - Chuhua Zhang
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1011 North University, Ann Arbor, MI, 48109-1078, USA
| | - Qian Xu
- Department of Biomedical Sciences and Center for Craniofacial Research and Diagnosis, Texas A&M University College of Dentistry, 3302 Gaston Ave., Dallas, TX, 75246, USA
| | - Yongbo Lu
- Department of Biomedical Sciences and Center for Craniofacial Research and Diagnosis, Texas A&M University College of Dentistry, 3302 Gaston Ave., Dallas, TX, 75246, USA
| | - Ling Qi
- Department of Molecular & Integrative Physiology, Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, 1000 Wall St., Ann Arbor, MI, 48105, USA
| | - Jan C-C Hu
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1011 North University, Ann Arbor, MI, 48109-1078, USA
| | - James P Simmer
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1011 North University, Ann Arbor, MI, 48109-1078, USA
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Chu KY, Wang YL, Chen JT, Lin CH, Yao CCJ, Chen YJ, Chen HW, Simmer JP, Hu JCC, Wang SK. PAX9 mutations and genetic synergism in familial tooth agenesis. Ann N Y Acad Sci 2023. [PMID: 37005710 DOI: 10.1111/nyas.14988] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/04/2023]
Abstract
Familial tooth agenesis (FTA) is one of the most common craniofacial anomalies in humans. Loss-of-function mutations in PAX9 and WNT10A have been known to cause FTA with various expressivity. In this study, we identified five FTA kindreds with novel PAX9 disease-causing mutations: p.(Glu7Lys), p.(Val83Leu), p.(Pro118Ser), p.(Ser197Argfs*23), and c.771+4A>G. Concomitant PAX9 and WNT10A pathogenic variants found in two probands with severe phenotypes suggested an effect of mutational synergism. All overexpressed PAX9s showed proper nuclear localization, excepting the p.(Pro118Ser) mutant. Various missense mutations caused differential loss of PAX9 transcriptional ability. PAX9 overexpression in dental pulp cells upregulated LEF1 and AXIN2 expression, indicating a positive regulatory role for PAX9 in canonical Wnt signaling. Analyzing 176 cases with 63 different mutations, we observed a distinct pattern of tooth agenesis for PAX9-associated FTA: Maxillary teeth are in general more frequently affected than mandibular ones. Along with all second molars, maxillary bicuspids and first molars are mostly involved, while maxillary lateral incisors and mandibular bicuspids are relatively less affected. Genotypically, missense mutations are associated with fewer missing teeth than frameshift and nonsense variants. This study significantly expands the phenotypic and genotypic spectrums of PAX9-associated disorders and reveals a molecular mechanism of genetic synergism underlying FTA variable expressivity.
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Affiliation(s)
- Kuan-Yu Chu
- Department of Dentistry, National Taiwan University School of Dentistry, Taipei City, Taiwan
- Department of Pediatric Dentistry, National Taiwan University Children's Hospital, Taipei City, Taiwan
| | - Yin-Lin Wang
- Department of Dentistry, National Taiwan University School of Dentistry, Taipei City, Taiwan
- Department of Pediatric Dentistry, National Taiwan University Children's Hospital, Taipei City, Taiwan
| | - Jung-Tsu Chen
- Department of Dentistry, National Taiwan University School of Dentistry, Taipei City, Taiwan
| | - Chia-Hui Lin
- Department of Dentistry, National Taiwan University School of Dentistry, Taipei City, Taiwan
| | - Chung-Chen Jane Yao
- Department of Dentistry, National Taiwan University School of Dentistry, Taipei City, Taiwan
| | - Yi-Jane Chen
- Department of Dentistry, National Taiwan University School of Dentistry, Taipei City, Taiwan
| | - Huan-Wen Chen
- Department of Pediatric Dentistry, National Taiwan University Children's Hospital, Taipei City, Taiwan
| | - James P Simmer
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, Michigan, USA
| | - Jan C-C Hu
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, Michigan, USA
| | - Shih-Kai Wang
- Department of Dentistry, National Taiwan University School of Dentistry, Taipei City, Taiwan
- Department of Pediatric Dentistry, National Taiwan University Children's Hospital, Taipei City, Taiwan
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Kim YJ, Zhang H, Lee Y, Seymen F, Koruyucu M, Kasimoglu Y, Simmer JP, Hu JCC, Kim JW. Novel WDR72 Mutations Causing Hypomaturation Amelogenesis Imperfecta. J Pers Med 2023; 13:326. [PMID: 36836560 PMCID: PMC9965932 DOI: 10.3390/jpm13020326] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2023] [Revised: 02/10/2023] [Accepted: 02/11/2023] [Indexed: 02/16/2023] Open
Abstract
Amelogenesis imperfecta (AI) is a heterogeneous collection of hereditary enamel defects. The affected enamel can be classified as hypoplastic, hypomaturation, or hypocalcified in form. A better understanding of normal amelogenesis and improvements in our ability to diagnose AI through genetic testing can be realized through more complete knowledge of the genes and disease-causing variants that cause AI. In this study, mutational analysis was performed with whole exome sequencing (WES) to identify genetic etiology underlying the hypomaturation AI condition in affected families. Mutational analyses identified biallelic WDR72 mutations in four hypomaturation AI families. Novel mutations include a homozygous deletion and insertion mutation (NM_182758.4: c.2680_2699delinsACTATAGTT, p.(Ser894Thrfs*15)), compound heterozygous mutations (paternal c.2332dupA, p.(Met778Asnfs*4)) and (maternal c.1287_1289del, p.(Ile430del)) and a homozygous 3694 bp deletion that includes exon 14 (NG_017034.2:g.96472_100165del). A homozygous recurrent mutation variant (c.1467_1468delAT, p.(Val491Aspfs*8)) was also identified. Current ideas on WDR72 structure and function are discussed. These cases expand the mutational spectrum of WDR72 mutations causing hypomaturation AI and improve the possibility of genetic testing to accurately diagnose AI caused by WDR72 defects.
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Affiliation(s)
- Youn Jung Kim
- Department of Pediatric Dentistry & DRI, School of Dentistry, Seoul National University, Seoul 03080, Republic of Korea
| | - Hong Zhang
- Department of Biologic and Materials Sciences & Prosthodontics, School of Dentistry, University of Michigan, Ann Arbor, MI 48109, USA
| | - Yejin Lee
- Department of Pediatric Dentistry & DRI, School of Dentistry, Seoul National University, Seoul 03080, Republic of Korea
| | - Figen Seymen
- Department of Paediatric Dentistry, Faculty of Dentistry, Altinbas University, Istanbul 34147, Turkey
| | - Mine Koruyucu
- Department of Pedodontics, Faculty of Dentistry, Istanbul University, Istanbul 34116, Turkey
| | - Yelda Kasimoglu
- Department of Pedodontics, Faculty of Dentistry, Istanbul University, Istanbul 34116, Turkey
| | - James P. Simmer
- Department of Biologic and Materials Sciences & Prosthodontics, School of Dentistry, University of Michigan, Ann Arbor, MI 48109, USA
| | - Jan C.-C. Hu
- Department of Biologic and Materials Sciences & Prosthodontics, School of Dentistry, University of Michigan, Ann Arbor, MI 48109, USA
| | - Jung-Wook Kim
- Department of Pediatric Dentistry & DRI, School of Dentistry, Seoul National University, Seoul 03080, Republic of Korea
- Department of Molecular Genetics & DRI, School of Dentistry, Seoul National University, Seoul 03080, Republic of Korea
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Liang T, Wang SK, Smith C, Zhang H, Hu Y, Seymen F, Koruyucu M, Kasimoglu Y, Kim JW, Zhang C, Saunders TL, Simmer JP, Hu JCC. Enamel defects in Acp4 R110C/R110C mice and human ACP4 mutations. Sci Rep 2022; 12:16477. [PMID: 36183038 PMCID: PMC9526733 DOI: 10.1038/s41598-022-20684-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Accepted: 09/16/2022] [Indexed: 11/13/2022] Open
Abstract
Human ACP4 (OMIM*606362) encodes a transmembrane protein that belongs to histidine acid phosphatase (ACP) family. Recessive mutations in ACP4 cause non-syndromic hypoplastic amelogenesis imperfecta (AI1J, OMIM#617297). While ACP activity has long been detected in developing teeth, its functions during tooth development and the pathogenesis of ACP4-associated AI remain largely unknown. Here, we characterized 2 AI1J families and identified a novel ACP4 disease-causing mutation: c.774_775del, p.Gly260Aspfs*29. To investigate the role of ACP4 during amelogenesis, we generated and characterized Acp4R110C mice that carry the p.(Arg110Cys) loss-of-function mutation. Mouse Acp4 expression was the strongest at secretory stage ameloblasts, and the protein localized primarily at Tomes' processes. While Acp4 heterozygous (Acp4+/R110C) mice showed no phenotypes, incisors and molars of homozygous (Acp4R110C/R110C) mice exhibited a thin layer of aplastic enamel with numerous ectopic mineralized nodules. Acp4R110C/R110C ameloblasts appeared normal initially but underwent pathology at mid-way of secretory stage. Ultrastructurally, sporadic enamel ribbons grew on mineralized dentin but failed to elongate, and aberrant needle-like crystals formed instead. Globs of organic matrix accumulated by the distal membranes of defective Tomes' processes. These results demonstrated a critical role for ACP4 in appositional growth of dental enamel probably by processing and regulating enamel matrix proteins around mineralization front apparatus.
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Affiliation(s)
- Tian Liang
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1011 N University Ave, Ann Arbor, MI, 48109, USA
| | - Shih-Kai Wang
- Department of Dentistry, National Taiwan University School of Dentistry, No. 1, Changde St., Zhongzheng Dist., Taipei City, 100, Taiwan
- Department of Pediatric Dentistry, National Taiwan University Children's Hospital, No. 8, Zhongshan S. Rd., Zhongzheng Dist., Taipei City, 100, Taiwan
| | - Charles Smith
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1011 N University Ave, Ann Arbor, MI, 48109, USA
- Department of Anatomy & Cell Biology, Faculty of Medicine & Health Sciences, McGill University, Montreal, QC, Canada
| | - Hong Zhang
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1011 N University Ave, Ann Arbor, MI, 48109, USA
| | - Yuanyuan Hu
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1011 N University Ave, Ann Arbor, MI, 48109, USA
| | - Figen Seymen
- Department of Pedodontics, Faculty of Dentistry, Altinbas University, 34147, Istanbul, Turkey
| | - Mine Koruyucu
- Department of Pedodontics, Faculty of Dentistry, Istanbul University, 34116, Istanbul, Turkey
| | - Yelda Kasimoglu
- Department of Pedodontics, Faculty of Dentistry, Istanbul University, 34116, Istanbul, Turkey
| | - Jung-Wook Kim
- Department of Molecular Genetics & Dental Research Institute, School of Dentistry, Seoul National University, Seoul, 03080, Republic of Korea
- Department of Pediatric Dentistry & Dental Research Institute, School of Dentistry, Seoul National University, Seoul, 03080, Republic of Korea
| | - Chuhua Zhang
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1011 N University Ave, Ann Arbor, MI, 48109, USA
| | - Thomas L Saunders
- Division of Molecular, Medicine and Genetics, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI, 48109, USA
| | - James P Simmer
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1011 N University Ave, Ann Arbor, MI, 48109, USA.
| | - Jan C-C Hu
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1011 N University Ave, Ann Arbor, MI, 48109, USA
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Kim YJ, Lee Y, Zhang H, Seymen F, Koruyucu M, Bayrak S, Tuloglu N, Simmer JP, Hu JCC, Kim JW. Translated Mutant DSPP mRNA Expression Level Impacts the Severity of Dentin Defects. J Pers Med 2022; 12:1002. [PMID: 35743786 PMCID: PMC9225647 DOI: 10.3390/jpm12061002] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Revised: 06/15/2022] [Accepted: 06/17/2022] [Indexed: 11/28/2022] Open
Abstract
Hereditary dentin defects are conventionally classified into three types of dentinogenesis imperfecta (DGI) and two types of dentin dysplasia (DD). Mutations in the dentin sialophosphoprotein (DSPP) gene have been identified to cause DGI type II and III and DD type II; therefore, these are not three different conditions, but rather allelic disorders. In this study, we recruited three families with varying clinical phenotypes from DGI-III to DD-II and performed mutational analysis by candidate gene analysis or whole-exome sequencing. Three novel mutations including a silent mutation (NM_014208.3: c.52-2del, c.135+1G>C, and c.135G>A; p.(Gln45=)) were identified, all of which affected pre-mRNA splicing. Comparison of the splicing assay results revealed that the expression level of the DSPP exon 3 deletion transcript correlated with the severity of the dentin defects. This study did not only expand the mutational spectrum of DSPP gene, but also advanced our understanding of the molecular pathogenesis impacting the severity of hereditary dentin defects.
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Affiliation(s)
- Youn Jung Kim
- Department of Pediatric Dentistry & DRI, School of Dentistry, Seoul National University, Seoul 03080, Korea; (Y.J.K.); (Y.L.)
| | - Yejin Lee
- Department of Pediatric Dentistry & DRI, School of Dentistry, Seoul National University, Seoul 03080, Korea; (Y.J.K.); (Y.L.)
| | - Hong Zhang
- Department of Biologic and Materials Sciences & Prosthodontics, School of Dentistry, University of Michigan, Ann Arbor, MI 48109, USA; (H.Z.); (J.P.S.); (J.C.-C.H.)
| | - Figen Seymen
- Department of Paediatric Dentistry, Faculty of Dentistry, Altinbas University, Istanbul 34147, Turkey;
| | - Mine Koruyucu
- Department of Pedodontics, Faculty of Dentistry, Istanbul University, Istanbul 34116, Turkey;
| | - Sule Bayrak
- Private Practice, Eskisehir 26150, Turkey; (S.B.); (N.T.)
| | - Nuray Tuloglu
- Private Practice, Eskisehir 26150, Turkey; (S.B.); (N.T.)
| | - James P. Simmer
- Department of Biologic and Materials Sciences & Prosthodontics, School of Dentistry, University of Michigan, Ann Arbor, MI 48109, USA; (H.Z.); (J.P.S.); (J.C.-C.H.)
| | - Jan C.-C. Hu
- Department of Biologic and Materials Sciences & Prosthodontics, School of Dentistry, University of Michigan, Ann Arbor, MI 48109, USA; (H.Z.); (J.P.S.); (J.C.-C.H.)
| | - Jung-Wook Kim
- Department of Pediatric Dentistry & DRI, School of Dentistry, Seoul National University, Seoul 03080, Korea; (Y.J.K.); (Y.L.)
- Department of Molecular Genetics & DRI, School of Dentistry, Seoul National University, Seoul 03080, Korea
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10
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Lee Y, Zhang H, Seymen F, Kim YJ, Kasimoglu Y, Koruyucu M, Simmer JP, Hu JCC, Kim JW. Novel KLK4 Mutations Cause Hypomaturation Amelogenesis Imperfecta. J Pers Med 2022; 12:jpm12020150. [PMID: 35207639 PMCID: PMC8878363 DOI: 10.3390/jpm12020150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Revised: 01/18/2022] [Accepted: 01/20/2022] [Indexed: 12/02/2022] Open
Abstract
Amelogenesis imperfecta (AI) is a group of rare genetic diseases affecting the tooth enamel. AI is characterized by an inadequate quantity and/or quality of tooth enamel and can be divided into three major categories: hypoplastic, hypocalcified and hypomaturation types. Even though there are some overlapping phenotypes, hypomaturation AI enamel typically has a yellow to brown discoloration with a dull appearance but a normal thickness indicating a less mineralized enamel matrix. In this study, we recruited four Turkish families with hypomaturation AI and performed mutational analysis using whole exome sequencing. These analyses revealed two novel homozygous mutations in the KLK4 gene: a nonsense mutation in exon 3 (NM_004917.4:c.170C>A, p.(Ser57*)) was found in families 1, 2 and 3 and a missense mutation in exon 6 (c.637T>C, p.(Cys213Arg)) in family 4. Functional analysis showed that the missense mutation transcript could not translate the mutant protein efficiently or generated an unstable protein that lacked functional activity. The two novel inactivating KLK4 mutations we identified caused a hypomaturation AI phenotype similar to those caused by the four previously described KLK4 nonsense and frameshift mutations. This study improves our understanding of the normal and pathologic mechanisms of enamel formation.
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Affiliation(s)
- Yejin Lee
- Department of Pediatric Dentistry, School of Dentistry & DRI, Seoul National University, Seoul 03080, Korea; (Y.L.); (Y.J.K.)
| | - Hong Zhang
- Department of Biologic and Materials Sciences & Prosthodontics, School of Dentistry, University of Michigan, Ann Arbor, MI 48109, USA; (H.Z.); (J.P.S.); (J.C.-C.H.)
| | - Figen Seymen
- Department of Pedodontics, Faculty of Dentistry, Istanbul University, Istanbul 34116, Turkey; (F.S.); (Y.K.); (M.K.)
| | - Youn Jung Kim
- Department of Pediatric Dentistry, School of Dentistry & DRI, Seoul National University, Seoul 03080, Korea; (Y.L.); (Y.J.K.)
| | - Yelda Kasimoglu
- Department of Pedodontics, Faculty of Dentistry, Istanbul University, Istanbul 34116, Turkey; (F.S.); (Y.K.); (M.K.)
| | - Mine Koruyucu
- Department of Pedodontics, Faculty of Dentistry, Istanbul University, Istanbul 34116, Turkey; (F.S.); (Y.K.); (M.K.)
| | - James P. Simmer
- Department of Biologic and Materials Sciences & Prosthodontics, School of Dentistry, University of Michigan, Ann Arbor, MI 48109, USA; (H.Z.); (J.P.S.); (J.C.-C.H.)
| | - Jan C.-C. Hu
- Department of Biologic and Materials Sciences & Prosthodontics, School of Dentistry, University of Michigan, Ann Arbor, MI 48109, USA; (H.Z.); (J.P.S.); (J.C.-C.H.)
| | - Jung-Wook Kim
- Department of Pediatric Dentistry, School of Dentistry & DRI, Seoul National University, Seoul 03080, Korea; (Y.L.); (Y.J.K.)
- Department of Molecular Genetics, School of Dentistry & DRI, Seoul National University, Seoul 03080, Korea
- Correspondence:
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11
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Seymen F, Zhang H, Kasimoglu Y, Koruyucu M, Simmer JP, Hu JCC, Kim JW. Novel Mutations in GPR68 and SLC24A4 Cause Hypomaturation Amelogenesis Imperfecta. J Pers Med 2021; 12:jpm12010013. [PMID: 35055328 PMCID: PMC8781920 DOI: 10.3390/jpm12010013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2021] [Revised: 12/15/2021] [Accepted: 12/20/2021] [Indexed: 11/16/2022] Open
Abstract
Amelogenesis imperfecta (AI) is a rare genetic condition affecting the quantity and/or quality of tooth enamel. Hypomaturation AI is characterized by brownish-yellow discoloration with increased opacity and poorly mineralized enamel prone to fracture and attrition. We recruited three families affected by hypomaturation AI and performed whole exome sequencing with selected individuals in each family. Bioinformatic analysis and Sanger sequencing identified and confirmed mutations and segregation in the families. Family 1 had a novel homozygous frameshift mutation in GPR68 gene (NM_003485.3:c.78_83delinsC, p.(Val27Cysfs*146)). Family 2 had a novel homozygous nonsense mutation in SLC24A4 gene (NM_153646.4:c.613C>T, NP_705932.2:p.(Arg205*)). Family 3 also had a homozygous missense mutation in SLC24A4 gene which was reported previously (c.437C>T, p.(Ala146Val)). This report not only expands the mutational spectrum of the AI-causing genes but also improves our understanding of normal and pathologic amelogenesis.
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Affiliation(s)
- Figen Seymen
- Department of Pedodontics, Faculty of Dentistry, Istanbul University, Istanbul 34116, Turkey; (F.S.); (Y.K.); (M.K.)
| | - Hong Zhang
- Department of Biologic and Materials Sciences & Prosthodontics, School of Dentistry, University of Michigan, Ann Arbor, MI 48109, USA; (H.Z.); (J.P.S.); (J.C.-C.H.)
| | - Yelda Kasimoglu
- Department of Pedodontics, Faculty of Dentistry, Istanbul University, Istanbul 34116, Turkey; (F.S.); (Y.K.); (M.K.)
| | - Mine Koruyucu
- Department of Pedodontics, Faculty of Dentistry, Istanbul University, Istanbul 34116, Turkey; (F.S.); (Y.K.); (M.K.)
| | - James P. Simmer
- Department of Biologic and Materials Sciences & Prosthodontics, School of Dentistry, University of Michigan, Ann Arbor, MI 48109, USA; (H.Z.); (J.P.S.); (J.C.-C.H.)
| | - Jan C.-C. Hu
- Department of Biologic and Materials Sciences & Prosthodontics, School of Dentistry, University of Michigan, Ann Arbor, MI 48109, USA; (H.Z.); (J.P.S.); (J.C.-C.H.)
| | - Jung-Wook Kim
- Department of Pediatric Dentistry, School of Dentistry & DRI, Seoul National University, Seoul 03080, Korea
- Department of Molecular Genetics, School of Dentistry & DRI, Seoul National University, Seoul 03080, Korea
- Correspondence:
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12
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Simmer JP, Hu JCC, Hu Y, Zhang S, Liang T, Wang SK, Kim JW, Yamakoshi Y, Chun YH, Bartlett JD, Smith CE. A genetic model for the secretory stage of dental enamel formation. J Struct Biol 2021; 213:107805. [PMID: 34715329 PMCID: PMC8665125 DOI: 10.1016/j.jsb.2021.107805] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Revised: 10/18/2021] [Accepted: 10/20/2021] [Indexed: 01/13/2023]
Abstract
The revolution in genetics has rapidly increased our knowledge of human and mouse genes that are critical for the formation of dental enamel and helps us understand how enamel evolved. In this graphical review we focus on the roles of 41 genes that are essential for the secretory stage of amelogenesis when characteristic enamel mineral ribbons initiate on dentin and elongate to expand the enamel layer to the future surface of the tooth. Based upon ultrastructural analyses of genetically modified mice, we propose a molecular model explaining how a cell attachment apparatus including collagen 17, α6ß4 and αvß6 integrins, laminin 332, and secreted enamel proteins could attach to individual enamel mineral ribbons and mold their cross-sectional dimensions as they simultaneously elongate and orient them in the direction of the retrograde movement of the ameloblast membrane.
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Affiliation(s)
- James P Simmer
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1011 North University, Ann Arbor, MI 48108, USA.
| | - Jan C-C Hu
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1011 North University, Ann Arbor, MI 48108, USA.
| | - Yuanyuan Hu
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1011 North University, Ann Arbor, MI 48108, USA.
| | - Shelly Zhang
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1011 North University, Ann Arbor, MI 48108, USA.
| | - Tian Liang
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1011 North University, Ann Arbor, MI 48108, USA.
| | - Shih-Kai Wang
- Department of Dentistry, National Taiwan University School of Dentistry, No. 1, Changde St., Zhongzheng Dist., Taipei City 100, Taiwan; Department of Pediatric Dentistry, National Taiwan University Children's Hospital, No. 8, Zhongshan S. Rd., Zhongzheng Dist., Taipei City 100, Taiwan.
| | - Jung-Wook Kim
- Department of Molecular Genetics, School of Dentistry & Dental Research Institute, Seoul National University, Seoul, Korea; Department of Pediatric Dentistry, School of Dentistry & Dental Research Institute, Seoul National University, Seoul, Korea.
| | - Yasuo Yamakoshi
- Department of Biochemistry and Molecular Biology, School of Dental Medicine, Tsurumi University, 2-1-3 Tsurumi, Tsurumi-ku, Yokohama 230-8501, Japan.
| | - Yong-Hee Chun
- Department of Periodontics, School of Dentistry, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA.
| | - John D Bartlett
- Division of Biosciences, Ohio State University College of Dentistry, Columbus, OH, USA.
| | - Charles E Smith
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1011 North University, Ann Arbor, MI 48108, USA; Department of Anatomy & Cell Biology, Faculty of Medicine & Health Sciences, McGill University, Montreal, Quebec H3A 0C7, Canada.
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13
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Chu KY, Wang YL, Chou YR, Chen JT, Wang YP, Simmer JP, Hu JCC, Wang SK. Synergistic Mutations of LRP6 and WNT10A in Familial Tooth Agenesis. J Pers Med 2021; 11:jpm11111217. [PMID: 34834569 PMCID: PMC8621929 DOI: 10.3390/jpm11111217] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2021] [Revised: 11/13/2021] [Accepted: 11/13/2021] [Indexed: 02/07/2023] Open
Abstract
Familial tooth agenesis (FTA), distinguished by developmental failure of selected teeth, is one of the most prevalent craniofacial anomalies in humans. Mutations in genes involved in WNT/β-catenin signaling, including AXIN2 WNT10A, WNT10B, LRP6, and KREMEN1, are known to cause FTA. However, mutational interactions among these genes have not been fully explored. In this study, we characterized four FTA kindreds with LRP6 pathogenic mutations: p.(Gln1252*), p.(Met168Arg), p.(Ala754Pro), and p.(Asn1075Ser). The three missense mutations were predicted to cause structural destabilization of the LRP6 protein. Two probands carrying both an LRP6 mutant allele and a WNT10A variant exhibited more severe phenotypes, suggesting mutational synergism or digenic inheritance. Biallelic LRP6 mutations in a patient with many missing teeth further supported the dose-dependence of LRP6-associated FTA. Analysis of 21 FTA cases with 15 different LRP6 loss-of-function mutations revealed high heterogeneity of disease severity and a distinctive pattern of missing teeth, with maxillary canines being frequently affected. We hypothesized that various combinations of sequence variants in WNT-related genes can modulate WNT signaling activities during tooth development and cause a wide spectrum of tooth agenesis severity, which highlights the importance of exome/genome analysis for the genetic diagnosis of FTA in this era of precision medicine.
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Affiliation(s)
- Kuan-Yu Chu
- Department of Dentistry, School of Dentistry, National Taiwan University, Taipei City 100, Taiwan; (K.-Y.C.); (Y.-L.W.); (J.-T.C.); (Y.-P.W.)
- Department of Pediatric Dentistry, National Taiwan University Children’s Hospital, Taipei City 100, Taiwan
| | - Yin-Lin Wang
- Department of Dentistry, School of Dentistry, National Taiwan University, Taipei City 100, Taiwan; (K.-Y.C.); (Y.-L.W.); (J.-T.C.); (Y.-P.W.)
- Department of Pediatric Dentistry, National Taiwan University Children’s Hospital, Taipei City 100, Taiwan
| | - Yu-Ren Chou
- Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei City 106, Taiwan;
| | - Jung-Tsu Chen
- Department of Dentistry, School of Dentistry, National Taiwan University, Taipei City 100, Taiwan; (K.-Y.C.); (Y.-L.W.); (J.-T.C.); (Y.-P.W.)
| | - Yi-Ping Wang
- Department of Dentistry, School of Dentistry, National Taiwan University, Taipei City 100, Taiwan; (K.-Y.C.); (Y.-L.W.); (J.-T.C.); (Y.-P.W.)
| | - James P. Simmer
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI 48108, USA; (J.P.S.); (J.C.-C.H.)
| | - Jan C.-C. Hu
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI 48108, USA; (J.P.S.); (J.C.-C.H.)
| | - Shih-Kai Wang
- Department of Dentistry, School of Dentistry, National Taiwan University, Taipei City 100, Taiwan; (K.-Y.C.); (Y.-L.W.); (J.-T.C.); (Y.-P.W.)
- Department of Pediatric Dentistry, National Taiwan University Children’s Hospital, Taipei City 100, Taiwan
- Correspondence: ; Tel.: +886-2-23123456 (ext. 70251)
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14
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Lee Y, Zhang H, Seymen F, Koruyucu M, Kasimoglu Y, Lee ZH, Hu JCC, Simmer JP, Kim JW. Novel homozygous KREMEN1 mutation causes ectodermal dysplasia. Oral Dis 2021; 28:843-845. [PMID: 34028942 DOI: 10.1111/odi.13921] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2020] [Revised: 05/03/2021] [Accepted: 05/09/2021] [Indexed: 11/29/2022]
Affiliation(s)
- Yejin Lee
- Department of Pediatric Dentistry, School of Dentistry & DRI, Seoul National University, Seoul, Korea
| | - Hong Zhang
- Department of Biologic and Materials Sciences, School of Dentistry, University of Michigan, Ann Arbor, MI, USA
| | - Figen Seymen
- Department of Pedodontics, Faculty of Dentistry, Istanbul University, Istanbul, Turkey
| | - Mine Koruyucu
- Department of Pedodontics, Faculty of Dentistry, Istanbul University, Istanbul, Turkey
| | - Yelda Kasimoglu
- Department of Pedodontics, Faculty of Dentistry, Istanbul University, Istanbul, Turkey
| | - Zang Hee Lee
- Department of Cell and Developmental Biology, School of Dentistry & DRI, Seoul National University, Seoul, Korea
| | - Jan C-C Hu
- Department of Biologic and Materials Sciences, School of Dentistry, University of Michigan, Ann Arbor, MI, USA
| | - James P Simmer
- Department of Biologic and Materials Sciences, School of Dentistry, University of Michigan, Ann Arbor, MI, USA
| | - Jung-Wook Kim
- Department of Pediatric Dentistry, School of Dentistry & DRI, Seoul National University, Seoul, Korea.,Department of Molecular Genetics, School of Dentistry & DRI, Seoul National University, Seoul, Korea
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15
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Bartlett JD, Smith CE, Hu Y, Ikeda A, Strauss M, Liang T, Hsu YH, Trout AH, McComb DW, Freeman RC, Simmer JP, Hu JCC. MMP20-generated amelogenin cleavage products prevent formation of fan-shaped enamel malformations. Sci Rep 2021; 11:10570. [PMID: 34012043 PMCID: PMC8134442 DOI: 10.1038/s41598-021-90005-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Accepted: 04/27/2021] [Indexed: 11/09/2022] Open
Abstract
Dental enamel forms extracellularly as thin ribbons of amorphous calcium phosphate (ACP) that initiate on dentin mineral in close proximity to the ameloblast distal membrane. Secreted proteins are critical for this process. Enam-/- and Ambn-/- mice fail to form enamel. We characterize enamel ribbon formation in wild-type (WT), Amelx-/- and Mmp20-/- mouse mandibular incisors using focused ion beam scanning electron microscopy (FIB-SEM) in inverted backscatter mode. In Amelx-/- mice, initial enamel mineral ribbons extending from dentin are similar in form to those of WT mice. As early enamel development progresses, the Amelx-/- mineral ribbons develop multiple branches, resembling the staves of a Japanese fan. These striking fan-shaped structures cease growing after attaining ~ 20 µm of enamel thickness (WT is ~ 120 µm). The initial enamel mineral ribbons in Mmp20-/- mice, like those of the Amelx-/- and WT, extend from the dentin surface to the ameloblast membrane, but appear to be fewer in number and coated on their sides with organic material. Remarkably, Mmp20-/- mineral ribbons also form fan-like structures that extend to ~ 20 µm from the dentin surface. However, these fans are subsequently capped with a hard, disorganized outer mineral layer. Amelogenin cleavage products are the only matrix components absent in both Amelx-/- and Mmp20-/- mice. We conclude that MMP20 and amelogenin are not critical for enamel mineral ribbon initiation, orientation, or initial shape. The pathological fan-like plates in these mice may form from the lack of amelogenin cleavage products, which appear necessary to form ordered hydroxyapatite.
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Affiliation(s)
- John D Bartlett
- Division of Biosciences, Ohio State University College of Dentistry, Columbus, OH, USA
| | - Charles E Smith
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1210 Eisenhower Pl, Ann Arbor, MI, 48108, USA
- Department of Anatomy and Cell Biology, Faculty of Medicine and Health Sciences, McGill University, Montreal, QC, Canada
| | - Yuanyuan Hu
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1210 Eisenhower Pl, Ann Arbor, MI, 48108, USA
| | - Atsushi Ikeda
- Division of Biosciences, Ohio State University College of Dentistry, Columbus, OH, USA
| | - Mike Strauss
- Department of Anatomy and Cell Biology, Faculty of Medicine and Health Sciences, McGill University, Montreal, QC, Canada
| | - Tian Liang
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1210 Eisenhower Pl, Ann Arbor, MI, 48108, USA
| | - Ya-Hsiang Hsu
- Department of Materials Science and Engineering, Ohio State University College of Engineering, Columbus, OH, USA
- Center for Electron Microscopy and Analysis, Ohio State University, Columbus, OH, USA
| | - Amanda H Trout
- Department of Materials Science and Engineering, Ohio State University College of Engineering, Columbus, OH, USA
- Center for Electron Microscopy and Analysis, Ohio State University, Columbus, OH, USA
| | - David W McComb
- Department of Materials Science and Engineering, Ohio State University College of Engineering, Columbus, OH, USA
- Center for Electron Microscopy and Analysis, Ohio State University, Columbus, OH, USA
| | - Rebecca C Freeman
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1210 Eisenhower Pl, Ann Arbor, MI, 48108, USA
| | - James P Simmer
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1210 Eisenhower Pl, Ann Arbor, MI, 48108, USA.
| | - Jan C-C Hu
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1210 Eisenhower Pl, Ann Arbor, MI, 48108, USA
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16
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Kim YJ, Lee Y, Zhang H, Song JS, Hu JCC, Simmer JP, Kim JW. A Novel De Novo SP6 Mutation Causes Severe Hypoplastic Amelogenesis Imperfecta. Genes (Basel) 2021; 12:346. [PMID: 33652941 PMCID: PMC7996877 DOI: 10.3390/genes12030346] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Revised: 02/26/2021] [Accepted: 02/26/2021] [Indexed: 12/15/2022] Open
Abstract
Amelogenesis imperfecta (AI) is a heterogeneous group of rare genetic disorders affecting tooth enamel formation. Here we report an identification of a novel de novo missense mutation [c.817_818delinsAT, p.(Ala273Met)] in the SP6 gene, causing non-syndromic autosomal dominant AI. This is the second paper on amelogenesis imperfecta caused by SP6 mutation. Interestingly the identified mutation in this study is a 2-bp variant at the same nucleotide positions as the first report, but with AT instead of AA insertion. Clinical phenotype was much more severe compared to the previous report, and western blot showed an extremely decreased level of mutant protein compared to the wild-type, even though the mRNA level was similar.
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Affiliation(s)
- Youn Jung Kim
- Department of Molecular Genetics & DRI, School of Dentistry, Seoul National University, Seoul 03080, Korea;
| | - Yejin Lee
- Department of Pediatric Dentistry & DRI, School of Dentistry, Seoul National University, Seoul 03080, Korea; (Y.L.); (J.-S.S.)
| | - Hong Zhang
- Department of Biologic and Materials Sciences, School of Dentistry, University of Michigan, Ann Arbor, MI 48108, USA; (H.Z.); (J.C.-C.H.); (J.P.S.)
| | - Ji-Soo Song
- Department of Pediatric Dentistry & DRI, School of Dentistry, Seoul National University, Seoul 03080, Korea; (Y.L.); (J.-S.S.)
| | - Jan C.-C. Hu
- Department of Biologic and Materials Sciences, School of Dentistry, University of Michigan, Ann Arbor, MI 48108, USA; (H.Z.); (J.C.-C.H.); (J.P.S.)
| | - James P. Simmer
- Department of Biologic and Materials Sciences, School of Dentistry, University of Michigan, Ann Arbor, MI 48108, USA; (H.Z.); (J.C.-C.H.); (J.P.S.)
| | - Jung-Wook Kim
- Department of Molecular Genetics & DRI, School of Dentistry, Seoul National University, Seoul 03080, Korea;
- Department of Pediatric Dentistry & DRI, School of Dentistry, Seoul National University, Seoul 03080, Korea; (Y.L.); (J.-S.S.)
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17
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Smith CE, Hu Y, Strauss M, Hu JCC, Simmer JP. The spatial distribution of focal stacks within the inner enamel layer of mandibular mouse incisors. J Anat 2020; 238:970-985. [PMID: 33145767 PMCID: PMC7930765 DOI: 10.1111/joa.13352] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 10/14/2020] [Accepted: 10/15/2020] [Indexed: 01/08/2023] Open
Abstract
Focal stacks are an alternative spatial arrangement of enamel rods within the inner enamel of mandibular mouse incisors where short rows comprised of 2–45 enamel rods are nestled at the side of much longer rows, both sharing the same rod tilt directed mesially or laterally. The significance of focal stacks to enamel function is unknown, but their high frequency in transverse sections (30% of all rows) suggests that they serve some purpose beyond representing an oddity of enamel development. In this study, we characterized the spatial distribution of focal stacks in random transverse sections relative to different regions of the inner enamel and to different locations across enamel thickness. The curving dentinoenamel junction (DEJ) in transverse sections complicated spatial distribution analyses, and a technique was developed to “unbend” the curving DEJ allowing for more linear quantitative analyses to be carried out. The data indicated that on average there were 36 ± 7 focal stacks located variably within the inner enamel in any given transverse section. Consistent with area distributions, focal stacks were four times more frequent in the lateral region (53%) and twice as frequent in the mesial region (33%) compared to the central region (14%). Focal stacks were equally split by tilt (52% mesial vs. 48% lateral, not significant), but those having a mesial tilt were more frequently encountered in the lateral and central regions (2:1) and those having a lateral tilt were more numerous in the mesial region (1:3). Focal stacks having a mesial tilt were longer on average compared to those having a lateral tilt (7.5 ± 5.6 vs. 5.9 ± 4.0 rods per row, p < 0.01). There was no relationship between the length of a focal stack and its location within the inner enamel. All results were consistent with the notion that focal stacks travel from the DEJ to the outer enamel the same as the longer and decussating companion rows to which they are paired. The spatial distribution of focal stacks within the inner enamel was not spatially random but best fit a null model based on a heterogenous Poisson point process dependent on regional location within the transverse plane of the enamel layer.
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Affiliation(s)
- Charles E Smith
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, USA.,Department of Anatomy & Cell Biology, Faculty of Medicine & Health Sciences, McGill University, Montreal, QC, Canada
| | - Yuanyuan Hu
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, USA
| | - Mike Strauss
- Department of Anatomy & Cell Biology, Faculty of Medicine & Health Sciences, McGill University, Montreal, QC, Canada.,Facility for Electron Microscopy Research, McGill University, Montreal, QC, Canada
| | - Jan C-C Hu
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, USA
| | - James P Simmer
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, USA
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Abstract
Autosomal dominant hypocalcified amelogenesis imperfecta (ADHCAI; OMIM #130900) is a genetic disorder exhibiting severe hardness defects and reduced fracture toughness of dental enamel. While the condition is nonsyndromic, it can be associated with other craniofacial anomalies, such as malocclusions and delayed or failed tooth eruption. Truncation mutations in FAM83H (OMIM *611927) are hitherto the sole cause of ADHCAI. With human genetic studies, Fam83h knockout and mutation-knock-in mouse models indicated that FAM83H does not serve a critical physiologic function during enamel formation and suggested a neomorphic mutation mechanism causing ADHCAI. The function of FAM83H remains obscure. FAM83H has been shown to interact with various isoforms of casein kinase 1 (CK1) and keratins and to mediate organization of keratin cytoskeletons and desmosomes. By considering FAM83H a scaffold protein to anchor CK1s, further molecular characterization of the protein could gain insight into its functions. In this study, we characterized 9 kindreds with ADHCAI and identified 3 novel FAM83H truncation mutations: p.His437*, p.Gln459*, and p.Glu610*. Some affected individuals exhibited hypoplastic phenotypes, in addition to the characteristic hypocalcification enamel defects, which have never been well documented. Failed eruption of canines or second molars in affected persons was observed in 4 of the families. The p.Glu610* mutation was located in a gap area (amino acids 470 to 625) within the zone of previously reported pathogenic variants (amino acids 287 to 694). In vitro pull-down studies with overexpressed FAM83H proteins in HEK293 cells demonstrated an interaction between FAM83H and SEC16A, a protein component of the COP II complex at endoplasmic reticulum exit sites. The interaction was mediated by the middle part (amino acids 287 to 657) of mouse FAM83H protein. Results of this study significantly extended the phenotypic and genotypic spectrums of FAM83H-associated ADHCAI and suggested a role for FAM83H in endoplasmic reticulum-to-Golgi vesicle trafficking and protein secretion (dbGaP phs001491.v1.p1).
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Affiliation(s)
- S K Wang
- Department of Biologic and Materials Sciences, School of Dentistry, University of Michigan, Ann Arbor, MI, USA.,Department of Dentistry, School of Dentistry, National Taiwan University, Jhongjheng District, Taipei City, Taiwan
| | - H Zhang
- Department of Biologic and Materials Sciences, School of Dentistry, University of Michigan, Ann Arbor, MI, USA
| | - C Y Hu
- Department of Prosthodontics, National Taiwan University Hospital, Jhongjheng District, Taipei City, Taiwan
| | - J F Liu
- Division of Pediatric Dentistry, Department of Stomatology, Taichung Veterans General Hospital, Xitun District, Taichung City, Taiwan
| | - S Chadha
- Department of Biologic and Materials Sciences, School of Dentistry, University of Michigan, Ann Arbor, MI, USA
| | - J W Kim
- Department of Pediatric Dentistry and Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Republic of Korea.,Department of Molecular Genetics and Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Republic of Korea
| | - J P Simmer
- Department of Biologic and Materials Sciences, School of Dentistry, University of Michigan, Ann Arbor, MI, USA
| | - J C C Hu
- Department of Biologic and Materials Sciences, School of Dentistry, University of Michigan, Ann Arbor, MI, USA
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19
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Wang SK, Zhang H, Chavez MB, Hu Y, Seymen F, Koruyucu M, Kasimoglu Y, Colvin CD, Kolli TN, Tan MH, Wang YL, Lu PY, Kim JW, Foster BL, Bartlett JD, Simmer JP, Hu JCC. Dental malformations associated with biallelic MMP20 mutations. Mol Genet Genomic Med 2020; 8:e1307. [PMID: 32495503 PMCID: PMC7434610 DOI: 10.1002/mgg3.1307] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Revised: 04/07/2020] [Accepted: 04/08/2020] [Indexed: 12/30/2022] Open
Abstract
Background Matrix metallopeptidase 20 (MMP20) is an evolutionarily conserved protease that is essential for processing enamel matrix proteins during dental enamel formation. MMP20 mutations cause human autosomal recessive pigmented hypomaturation‐type amelogenesis imperfecta (AI2A2; OMIM #612529). MMP20 is expressed in both odontoblasts and ameloblasts, but its function during dentinogenesis is unclear. Methods We characterized 10 AI kindreds with MMP20 defects, characterized human third molars and/or Mmp20−/− mice by histology, Backscattered Scanning Electron Microscopy (bSEM), µCT, and nanohardness testing. Results We identified six novel MMP20 disease‐causing mutations. Four pathogenic variants were associated with exons encoding the MMP20 hemopexin‐like (PEX) domain, suggesting a necessary regulatory function. Mutant human enamel hardness was softest (13% of normal) midway between the dentinoenamel junction (DEJ) and the enamel surface. bSEM and µCT analyses of the third molars revealed reduced mineral density in both enamel and dentin. Dentin close to the DEJ showed an average hardness number 62%–69% of control. Characterization of Mmp20−/− mouse dentin revealed a significant reduction in dentin thickness and mineral density and a transient increase in predentin thickness, indicating disturbances in dentin matrix secretion and mineralization. Conclusion These results expand the spectrum of MMP20 disease‐causing mutations and provide the first evidence for MMP20 function during dentin formation.
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Affiliation(s)
- Shih-Kai Wang
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, USA.,Department of Pediatric Dentistry, National Taiwan University School of Dentistry, Taipei City, Taiwan R.O.C
| | - Hong Zhang
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, USA
| | - Michael B Chavez
- Division of Biosciences, College of Dentistry, The Ohio State University, Columbus, OH, USA
| | - Yuanyuan Hu
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, USA
| | - Figen Seymen
- Department of Pedodontics, Istanbul University Faculty of Dentistry, Istanbul, Turkey
| | - Mine Koruyucu
- Department of Pedodontics, Istanbul University Faculty of Dentistry, Istanbul, Turkey
| | - Yelda Kasimoglu
- Department of Pedodontics, Istanbul University Faculty of Dentistry, Istanbul, Turkey
| | - Connor D Colvin
- Division of Biosciences, College of Dentistry, The Ohio State University, Columbus, OH, USA
| | - Tamara N Kolli
- Division of Biosciences, College of Dentistry, The Ohio State University, Columbus, OH, USA
| | - Michelle H Tan
- Division of Biosciences, College of Dentistry, The Ohio State University, Columbus, OH, USA
| | - Yin-Lin Wang
- Department of Pediatric Dentistry, National Taiwan University School of Dentistry, Taipei City, Taiwan R.O.C
| | - Pei-Ying Lu
- Department of Pediatric Dentistry, National Taiwan University School of Dentistry, Taipei City, Taiwan R.O.C
| | - Jung-Wook Kim
- Department of Pediatric Dentistry & Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Republic of Korea.,Department of Molecular Genetics & Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Republic of Korea
| | - Brian L Foster
- Division of Biosciences, College of Dentistry, The Ohio State University, Columbus, OH, USA
| | - John D Bartlett
- Division of Biosciences, College of Dentistry, The Ohio State University, Columbus, OH, USA
| | - James P Simmer
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, USA
| | - Jan C-C Hu
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, USA
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20
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Shin NY, Yamazaki H, Beniash E, Yang X, Margolis SS, Pugach MK, Simmer JP, Margolis HC. Amelogenin phosphorylation regulates tooth enamel formation by stabilizing a transient amorphous mineral precursor. J Biol Chem 2020; 295:1943-1959. [PMID: 31919099 DOI: 10.1074/jbc.ra119.010506] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Revised: 12/30/2019] [Indexed: 11/06/2022] Open
Abstract
Dental enamel comprises interwoven arrays of extremely long and narrow crystals of carbonated hydroxyapatite called enamel rods. Amelogenin (AMELX) is the predominant extracellular enamel matrix protein and plays an essential role in enamel formation (amelogenesis). Previously, we have demonstrated that full-length AMELX forms higher-order supramolecular assemblies that regulate ordered mineralization in vitro, as observed in enamel rods. Phosphorylation of the sole AMELX phosphorylation site (Ser-16) in vitro greatly enhances its capacity to stabilize amorphous calcium phosphate (ACP), the first mineral phase formed in developing enamel, and prevents apatitic crystal formation. To test our hypothesis that AMELX phosphorylation is critical for amelogenesis, we generated and characterized a hemizygous knockin (KI) mouse model with a phosphorylation-defective Ser-16 to Ala-16 substitution in AMELX. Using EM analysis, we demonstrate that in the absence of phosphorylated AMELX, KI enamel lacks enamel rods, the hallmark component of mammalian enamel, and, unlike WT enamel, appears to be composed of less organized arrays of shorter crystals oriented normal to the dentinoenamel junction. KI enamel also exhibited hypoplasia and numerous surface defects, whereas heterozygous enamel displayed highly variable mosaic structures with both KI and WT features. Importantly, ACP-to-apatitic crystal transformation occurred significantly faster in KI enamel. Secretory KI ameloblasts also lacked Tomes' processes, consistent with the absence of enamel rods, and underwent progressive cell pathology throughout enamel development. In conclusion, AMELX phosphorylation plays critical mechanistic roles in regulating ACP-phase transformation and enamel crystal growth, and in maintaining ameloblast integrity and function during amelogenesis.
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Affiliation(s)
- Nah-Young Shin
- The Forsyth Institute, Cambridge, Massachusetts 02142; Department of Developmental Biology, Harvard School of Dental Medicine, Boston, Massachusetts 02115
| | - Hajime Yamazaki
- The Forsyth Institute, Cambridge, Massachusetts 02142; Department of Developmental Biology, Harvard School of Dental Medicine, Boston, Massachusetts 02115; Department of Oral Biology, Center for Craniofacial Regeneration, University of Pittsburgh, School of Dental Medicine, Pittsburgh, Pennsylvania 15213
| | - Elia Beniash
- Department of Oral Biology, Center for Craniofacial Regeneration, University of Pittsburgh, School of Dental Medicine, Pittsburgh, Pennsylvania 15213
| | - Xu Yang
- Department of Oral Biology, Center for Craniofacial Regeneration, University of Pittsburgh, School of Dental Medicine, Pittsburgh, Pennsylvania 15213
| | - Seth S Margolis
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Megan K Pugach
- The Forsyth Institute, Cambridge, Massachusetts 02142; Department of Developmental Biology, Harvard School of Dental Medicine, Boston, Massachusetts 02115
| | - James P Simmer
- Department of Biologic and Material Sciences, University of Michigan School of Dentistry, Ann Arbor, Michigan 48108
| | - Henry C Margolis
- The Forsyth Institute, Cambridge, Massachusetts 02142; Department of Developmental Biology, Harvard School of Dental Medicine, Boston, Massachusetts 02115; Department of Periodontics and Preventive Dentistry, Center for Craniofacial Regeneration, University of Pittsburgh, School of Dental Medicine, Pittsburgh, Pennsylvania 15213.
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21
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Zhang H, Hu Y, Seymen F, Koruyucu M, Kasimoglu Y, Wang S, Wright JT, Havel MW, Zhang C, Kim J, Simmer JP, Hu JC. ENAM mutations and digenic inheritance. Mol Genet Genomic Med 2019; 7:e00928. [PMID: 31478359 PMCID: PMC6785452 DOI: 10.1002/mgg3.928] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Revised: 07/25/2019] [Accepted: 07/26/2019] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND ENAM mutations cause autosomal dominant or recessive amelogenesis imperfecta (AI) and show a dose effect: enamel malformations are more severe or only penetrant when both ENAM alleles are defective. METHODS Whole exome sequences of recruited AI probands were initially screened for mutations in known AI candidate genes. Sanger sequencing was used to confirm sequence variations and their segregation with the disease phenotype. The co-occurrence of ENAM and LAMA3 mutations in one family raised the possibility of digenic inheritance. Enamel formed in Enam+/+ Ambn+/+ , Enam+/- , Ambn+/- , and Enam+/- Ambn+/- mice was characterized by dissection and backscattered scanning electron microscopy (bSEM). RESULTS ENAM mutations segregating with AI in five families were identified. Two novel ENAM frameshift mutations were identified. A single-nucleotide duplication (c.395dupA/p.Pro133Alafs*13) replaced amino acids 133-1142 with a 12 amino acid (ATTKAAFEAAIT*) sequence, and a single-nucleotide deletion (c.2763delT/p.Asp921Glufs*32) replaced amino acids 921-1142 with 31 amino acids (ESSPQQASYQAKETAQRRGKAKTLLEMMCPR*). Three families were heterozygous for a previously reported single-nucleotide ENAM deletion (c.588+1delG/p.Asn197Ilefs*81). One of these families also harbored a heterozygous LAMA3 mutation (c.1559G>A/p.Cys520Tyr) that cosegregated with both the AI phenotype and the ENAM mutation. In mice, Ambn+/- maxillary incisors were normal. Ambn+/- molars were also normal, except for minor surface roughness. Ambn+/- mandibular incisors were sometimes chalky and showed minor chipping. Enam+/- incisor enamel was thinner than normal with ectopic mineral deposited laterally. Enam+/- molars were sometimes chalky and rough surfaced. Enam+/- Ambn+/- enamel was thin and rough, in part due to ectopic mineralization, but also underwent accelerated attrition. CONCLUSION Novel ENAM mutations causing AI were identified, raising to 22 the number of ENAM variations known to cause AI. The severity of the enamel phenotype in Enam+/- Ambn+/- double heterozygous mice is caused by composite digenic effects. Digenic inheritance should be explored as a cause of AI in humans.
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Affiliation(s)
- Hong Zhang
- Department of Biologic and Materials SciencesUniversity of Michigan School of DentistryAnn ArborMIUSA
| | - Yuanyuan Hu
- Department of Biologic and Materials SciencesUniversity of Michigan School of DentistryAnn ArborMIUSA
| | - Figen Seymen
- Department of Pedodontics, Faculty of DentistryIstanbul UniversityIstanbulTurkey
| | - Mine Koruyucu
- Department of Pedodontics, Faculty of DentistryIstanbul UniversityIstanbulTurkey
| | - Yelda Kasimoglu
- Department of Pedodontics, Faculty of DentistryIstanbul UniversityIstanbulTurkey
| | - Shih‐Kai Wang
- Department of Biologic and Materials SciencesUniversity of Michigan School of DentistryAnn ArborMIUSA
- Department of DentistryNational Taiwan University School of DentistryTaipei CityTaiwan R.O.C.
| | - John Timothy Wright
- Department of Pediatric DentistryUniversity of North Carolina School of DentistryChapel HillNCUSA
| | - Michael W. Havel
- Department of Biologic and Materials SciencesUniversity of Michigan School of DentistryAnn ArborMIUSA
| | - Chuhua Zhang
- Department of Biologic and Materials SciencesUniversity of Michigan School of DentistryAnn ArborMIUSA
| | - Jung‐Wook Kim
- Department of Molecular Genetics and Department of Pediatric Dentistry and Dental Research Institute, School of DentistrySeoul National UniversitySeoulKorea
| | - James P. Simmer
- Department of Biologic and Materials SciencesUniversity of Michigan School of DentistryAnn ArborMIUSA
| | - Jan C.‐C. Hu
- Department of Biologic and Materials SciencesUniversity of Michigan School of DentistryAnn ArborMIUSA
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22
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Liang T, Hu Y, Smith CE, Richardson AS, Zhang H, Yang J, Lin B, Wang S, Kim J, Chun Y, Simmer JP, Hu JC. AMBN mutations causing hypoplastic amelogenesis imperfecta and Ambn knockout-NLS-lacZ knockin mice exhibiting failed amelogenesis and Ambn tissue-specificity. Mol Genet Genomic Med 2019; 7:e929. [PMID: 31402633 PMCID: PMC6732285 DOI: 10.1002/mgg3.929] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Revised: 07/25/2019] [Accepted: 07/26/2019] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND Ameloblastin (AMBN) is a secreted matrix protein that is critical for the formation of dental enamel and is enamel-specific with respect to its essential functions. Biallelic AMBN defects cause non-syndromic autosomal recessive amelogenesis imperfecta. Homozygous Ambn mutant mice expressing an internally truncated AMBN protein deposit only a soft mineral crust on the surface of dentin. METHODS We characterized a family with hypoplastic amelogenesis imperfecta caused by AMBN compound heterozygous mutations (c.1061T>C; p.Leu354Pro/ c.1340C>T; p.Pro447Leu). We generated and characterized Ambn knockout/NLS-lacZ (AmbnlacZ/lacZ ) knockin mice. RESULTS No AMBN protein was detected using immunohistochemistry in null mice. ß-galactosidase activity was specific for ameloblasts in incisors and molars, and islands of cells along developing molar roots. AmbnlacZ/lacZ 7-week incisors and unerupted (D14) first molars showed extreme enamel surface roughness. No abnormalities were observed in dentin mineralization or in nondental tissues. Ameloblasts in the AmbnlacZ/lacZ mice were unable to initiate appositional growth and started to degenerate and deposit ectopic mineral. No layer of initial enamel ribbons formed in the AmbnlacZ/lacZ mice, but pockets of amelogenin accumulated on the dentin surface along the ameloblast distal membrane and within the enamel organ epithelia (EOE). NLS-lacZ signal was positive in the epididymis and nasal epithelium, but negative in ovary, oviduct, uterus, prostate, seminal vesicles, testis, submandibular salivary gland, kidney, liver, bladder, and bone, even after 15 hr of incubation with X-gal. CONCLUSIONS Ameloblastin is critical for the initiation of enamel ribbon formation, and its absence results in pathological mineralization within the enamel organ epithelia.
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Affiliation(s)
- Tian Liang
- Department of Biologic and Materials SciencesUniversity of Michigan School of DentistryAnn ArborMichigan
| | - Yuanyuan Hu
- Department of Biologic and Materials SciencesUniversity of Michigan School of DentistryAnn ArborMichigan
| | - Charles E. Smith
- Department of Anatomy and Cell Biology, Faculty of MedicineMcGill UniversityMontrealQuebecCanada
| | - Amelia S Richardson
- Department of Biologic and Materials SciencesUniversity of Michigan School of DentistryAnn ArborMichigan
| | - Hong Zhang
- Department of Biologic and Materials SciencesUniversity of Michigan School of DentistryAnn ArborMichigan
| | - Jie Yang
- Department of Biologic and Materials SciencesUniversity of Michigan School of DentistryAnn ArborMichigan
- Department of Pediatric Dentistry, School and Hospital of StomatologyPeking UniversityBeijingChina
| | - Brent Lin
- Department of Orofacial SciencesUCSF School of DentistrySan FranciscoCalifornia
| | - Shih‐Kai Wang
- Department of DentistryNational Taiwan University School of DentistryTaipei CityTaiwan R.O.C
| | - Jung‐Wook Kim
- Department of Molecular Genetics and Department of Pediatric Dentistry & Dental Research Institute, School of DentistrySeoul National UniversitySeoulKorea
| | - Yong‐Hee Chun
- Department of Periodontics and Department of Cell Systems & Anatomy, School of DentistryUniversity of Texas Health Science Center at San AntonioSan AntonioTexas
| | - James P. Simmer
- Department of Biologic and Materials SciencesUniversity of Michigan School of DentistryAnn ArborMichigan
| | - Jan C.‐C. Hu
- Department of Biologic and Materials SciencesUniversity of Michigan School of DentistryAnn ArborMichigan
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23
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Smith CE, Hu Y, Hu JCC, Simmer JP. Characteristics of the transverse 2D uniserial arrangement of rows of decussating enamel rods in the inner enamel layer of mouse mandibular incisors. J Anat 2019; 235:912-930. [PMID: 31402450 PMCID: PMC6794213 DOI: 10.1111/joa.13053] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/06/2019] [Indexed: 12/16/2022] Open
Abstract
The 2D arrangement of rows of enamel rods with alternating (decussating) tilt angles across the thickness of the inner layer in rat and mouse incisor enamel is well known and assumed to occur in a uniform and repetitive pattern. Some irregularities in the arrangement of rows have been reported, but no detailed investigation of row structure across the entire inner enamel layer currently exists. This investigation was undertaken to determine if the global row pattern in mouse mandibular incisor enamel is predominately regular in nature with only occasional anomalies or if rows of enamel rods have more spatial complexity than previously suspected. The data from this investigation indicate that rows of enamel rods are highly variable in length and have complex transverse arrangements across the width and thickness of the inner enamel layer. The majority of rows are short or medium in length, with 87% having < 100 rods per row. The remaining 13% are long rows (with 100-233 rods per row) that contain 46% of all enamel rods seen in transverse sections. Variable numbers of rows were associated with the lateral, central and mesial regions of the enamel layer. Each region contained different ratios of short, medium and long rows. A variety of relationships was found along the transverse length of rows in each region, including uniform associations of alternating rod tilts between neighboring rows, and instances where two rows having the same rod tilt were paired for variable distances then moved apart to accommodate rows of opposite tilt. Sometimes a row appeared to branch into two rows with the same tilt, or conversely where two rows merged into one row depending upon the mesial-to-lateral direction in which the row was viewed. Some rows showed both pairing and branching/merging along their length. These tended to be among the longest rows identified, and they often crossed the central region with extensions into the lateral and mesial regions. The most frequent row arrangement was a row of petite length nestled at the side of another row having the same rod tilt (30% of all rows). These were termed 'focal stacks' and may relate to the evolution of uniserial rat and mouse incisor enamel from a multilayered ancestor. The mesial and lateral endpoints of rows also showed complex arrangements with the dentinoenamel junction (DEJ), the inner enamel layer itself, and the boundary area to the outer enamel layer. It was concluded that the diversity in row lengths and various spatial arrangements both within and between rows across the transverse plane provides a method to interlock the enamel layer across each region and keep the enamel layer compact relative to the curving DEJ surface. The uniserial pattern for rows in mouse mandibular incisors is not uniform, but diverse and very complex.
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Affiliation(s)
- Charles E Smith
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, USA.,Department of Anatomy & Cell Biology, Faculty of Medicine, McGill University, Montreal, QC, Canada
| | - Yuanyuan Hu
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, USA
| | - Jan C-C Hu
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, USA
| | - James P Simmer
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, USA
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24
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Wang YP, Lin HY, Zhong WL, Simmer JP, Wang SK. Transcriptome analysis of gingival tissues of enamel-renal syndrome. J Periodontal Res 2019; 54:653-661. [PMID: 31131889 DOI: 10.1111/jre.12666] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2019] [Revised: 04/08/2019] [Accepted: 04/12/2019] [Indexed: 12/17/2022]
Abstract
BACKGROUND AND OBJECTIVE Biallelic loss-of-function mutations of human FAM20A have been known to cause enamel-renal syndrome (ERS), featured by agenesis of dental enamel, nephrocalcinosis, and other orodental abnormalities, including gingival hyperplasia. However, while the histopathology of this gingival anomaly has been analyzed, its underlying molecular mechanism remains largely unknown. This study aimed to unravel the pathogenesis of gingival hyperplasia in ERS. METHODS Whole-exome sequencing was conducted for an ERS case. Transcriptome analyses, using RNA sequencing, of the patient's gingiva were performed to unravel dysregulated molecules and aberrant biological processes underlying the gingival pathology of ERS, which was further confirmed by histology and immunohistochemistry. RESULTS Two novel frameshift FAM20A mutations in Exon 1 (g.5417delG; c.129delG; p.Cys44Alafs*101) and Exon 5 (g.62248_62249delAG; c.734_735delAG; p.Glu245Glyfs*11) were identified. Transcriptional profiling of patient's gingival tissue revealed a total of 1683 genes whose expression had increased (1129 genes) or decreased (554 genes) at least 2-fold compared to control gingival tissues. There were 951 gene ontology (GO) terms of biological process being significantly over-represented or under-represented. While GOs involved in extracellular matrix organization, angiogenesis, biomineralization, and epithelial cell proliferation appeared to be activated in ERS gingiva, genes related to keratinocyte differentiation, epithelial development, and keratinization were of decreased expression. FAM20A immunohistochemistry revealed a strong reactivity at the suprabasal layers of epithelium in control gingiva but showed a significantly diminished and scattered signal in ERS tissues. For genes showing significant over-expression in the transcriptome analyses, namely ALPL, SPARC, and ACTA2, an increased immunoreactivity was observed. CONCLUSION Our results unraveled a potential role for FAM20A in homeostasis of both gingival epithelium and connective tissues.
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Affiliation(s)
- Yi-Ping Wang
- Department of Dentistry, School of Dentistry, National Taiwan University, Taipei City, Taiwan.,Graduate Institute of Clinical Dentistry, School of Dentistry, National Taiwan University, Taipei City, Taiwan
| | - Hung-Ying Lin
- Department of Oral and Maxillofacial Surgery, National Taiwan University Hospital, Taipei City, Taiwan
| | - Wen-Lan Zhong
- Department of Dentistry, School of Dentistry, National Taiwan University, Taipei City, Taiwan
| | - James P Simmer
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, Michigan
| | - Shih-Kai Wang
- Department of Dentistry, School of Dentistry, National Taiwan University, Taipei City, Taiwan.,Department of Pediatric Dentistry, National Taiwan University Children's Hospital, Taipei City, Taiwan
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25
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Wang SK, Hu Y, Smith CE, Yang J, Zeng C, Kim JW, Hu JCC, Simmer JP. The Enamel Phenotype in Homozygous Fam83h Truncation Mice. Mol Genet Genomic Med 2019; 7:e724. [PMID: 31060110 PMCID: PMC6565571 DOI: 10.1002/mgg3.724] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Revised: 03/14/2019] [Accepted: 04/08/2019] [Indexed: 12/27/2022] Open
Abstract
BACKGROUND Truncation FAM83H mutations cause human autosomal dominant hypocalcified amelogenesis imperfecta (ADHCAI), an inherited disorder characterized by severe hardness defects in dental enamel. No enamel defects were observed in Fam83h null mice suggesting that Fam83h truncation mice would better replicate human mutations. METHODS We generated and characterized a mouse model (Fam83hTr/Tr ) expressing a truncated FAM83H protein (amino acids 1-296), which recapitulated the ADHCAI-causing human FAM83H p.Tyr297* mutation. RESULTS Day 14 and 7-week Fam83hTr/Tr molars exhibited rough enamel surfaces and slender cusps resulting from hypoplastic enamel defects. The lateral third of the Fam83hTr/Tr incisor enamel layer was thinner, with surface roughness and altered enamel rod orientation, suggesting disturbed enamel matrix secretion. Regular electron density in mandibular incisor enamel indicated normal enamel maturation. Only mildly increased posteruption attrition of Fam83hTr/Tr molar enamel was observed at 7-weeks. Histologically, the Fam83hTr/Tr enamel organ, including ameloblasts, and enamel matrices at sequential stages of amelogenesis exhibited comparable morphology without overt abnormalities, except irregular and less evident ameloblast Tomes' processes in specific areas. CONCLUSIONS Considering Fam83h-/- mice showed no enamel phenotype, while Fam83hTr/Tr (p.Tyr297*) mice displayed obvious enamel malformations, we conclude that FAM83H truncation mutations causing ADHCAI in humans disturb amelogenesis through a neomorphic mechanism, rather than haploinsufficiency.
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Affiliation(s)
- Shih-Kai Wang
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, Michigan
| | - Yuanyuan Hu
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, Michigan
| | - Charles E Smith
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, Michigan.,Department of Anatomy and Cell Biology, McGill University, Quebec, Canada
| | - Jie Yang
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, Michigan
| | - Chunhua Zeng
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, Michigan
| | - Jung-Wook Kim
- Department of Pediatric Dentistry & Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea
| | - Jan C-C Hu
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, Michigan
| | - James P Simmer
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, Michigan
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Kim J, Zhang H, Seymen F, Koruyucu M, Hu Y, Kang J, Kim YJ, Ikeda A, Kasimoglu Y, Bayram M, Zhang C, Kawasaki K, Bartlett JD, Saunders TL, Simmer JP, Hu JC. Mutations in RELT cause autosomal recessive amelogenesis imperfecta. Clin Genet 2019; 95:375-383. [PMID: 30506946 PMCID: PMC6392136 DOI: 10.1111/cge.13487] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Revised: 11/26/2018] [Accepted: 11/27/2018] [Indexed: 12/16/2022]
Abstract
Amelogenesis imperfecta (AI) is a collection of isolated (non-syndromic) inherited diseases affecting dental enamel formation or a clinical phenotype in syndromic conditions. We characterized three consanguineous AI families with generalized irregular hypoplastic enamel with rapid attrition that perfectly segregated with homozygous defects in a novel gene: RELT that is a member of the tumor necrosis factor receptor superfamily (TNFRSF). RNAscope in situ hybridization of wild-type mouse molars and incisors showed specific Relt mRNA expression by secretory stage ameloblasts and by odontoblasts. Relt-/- mice generated by CRISPR/Cas9 exhibited incisor and molar enamel malformations. Relt-/- enamel had a rough surface and underwent rapid attrition. Normally unmineralized spaces in the deep enamel near the dentino-enamel junction (DEJ) were as highly mineralized as the adjacent enamel, which likely altered the mechanical properties of the DEJ. Phylogenetic analyses showed the existence of selective pressure on RELT gene outside of tooth development, indicating that the human condition may be syndromic, which possibly explains the history of small stature and severe childhood infections in two of the probands. Knowing a TNFRSF member is critical during the secretory stage of enamel formation advances our understanding of amelogenesis and improves our ability to diagnose human conditions featuring enamel malformations.
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Affiliation(s)
- Jung‐Wook Kim
- Department of Pediatric Dentistry & Dental Research Institute, School of DentistrySeoul National UniversitySeoulRepublic of Korea
- Department of Molecular Genetics & the Dental Research Institute, School of DentistrySeoul National UniversitySeoulRepublic of Korea
| | - Hong Zhang
- Department of Biologic and Materials SciencesUniversity of Michigan School of DentistryAnn ArborMichigan
| | - Figen Seymen
- Department of Pedodontics, Faculty of DentistryIstanbul UniversityIstanbulTurkey
| | - Mine Koruyucu
- Department of Pedodontics, Faculty of DentistryIstanbul UniversityIstanbulTurkey
| | - Yuanyuan Hu
- Department of Biologic and Materials SciencesUniversity of Michigan School of DentistryAnn ArborMichigan
| | - Jenny Kang
- Department of Pediatric Dentistry & Dental Research Institute, School of DentistrySeoul National UniversitySeoulRepublic of Korea
| | - Youn J. Kim
- Department of Molecular Genetics & the Dental Research Institute, School of DentistrySeoul National UniversitySeoulRepublic of Korea
| | - Atsushi Ikeda
- Division of BiosciencesThe Ohio State University, College of DentistryColumbusOhio
| | - Yelda Kasimoglu
- Department of Pedodontics, Faculty of DentistryIstanbul UniversityIstanbulTurkey
| | - Merve Bayram
- Department of Pedodontics, Faculty of DentistryIstanbul Medipol UniversityIstanbulTurkey
| | - Chuhua Zhang
- Department of Biologic and Materials SciencesUniversity of Michigan School of DentistryAnn ArborMichigan
| | - Kazuhiko Kawasaki
- Department of AnthropologyPenn State UniversityUniversity ParkPennsylvania
| | - John D. Bartlett
- Division of BiosciencesThe Ohio State University, College of DentistryColumbusOhio
| | - Thomas L. Saunders
- Department of Internal Medicine, Division of Molecular, Medicine and GeneticsUniversity of Michigan Medical SchoolAnn ArborMichigan
| | - James P. Simmer
- Department of Biologic and Materials SciencesUniversity of Michigan School of DentistryAnn ArborMichigan
| | - Jan C‐C. Hu
- Department of Biologic and Materials SciencesUniversity of Michigan School of DentistryAnn ArborMichigan
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Smith CE, Hu Y, Hu JC, Simmer JP. Quantitative analysis of the core 2D arrangement and distribution of enamel rods in cross-sections of mandibular mouse incisors. J Anat 2019; 234:274-290. [PMID: 30426488 PMCID: PMC6326826 DOI: 10.1111/joa.12912] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/15/2018] [Indexed: 02/02/2023] Open
Abstract
Considerable descriptive information about the overall organization of mouse mandibular incisor enamel is available but almost nothing is known about the quantitative characteristics of enamel rod arrangement and distribution in these teeth. This has important implications concerning cell movement during the secretory stage because each ameloblast makes one enamel rod. Knowing how many enamel rods are cut open in a cross-section of the enamel layer could provide insights into understanding the dynamics of how groups of ameloblasts form the enamel layer. In this study, cross-sections of fully mineralized enamel were cut on 24 mandibular mouse incisors, polished and etched, and imaged by scanning electron microscopy in backscatter mode. Montaged maps of the entire enamel layer were made at high magnification and the enamel rod profiles in each map were color-coded based upon rod category. Quantitative analyses of each color layer in the maps were then performed using standard routines available in imagej. The data indicated that that there were on average 7233 ± 575 enamel rod profiles per cross-section in mandibular incisors of 7-week-old mice, with 70% located in the inner enamel layer, 27% located in the outer enamel layer, and 3% positioned near the mesial and lateral cementoenamel junctions. All enamel rod profiles showed progressive increases in tilt angles, some very large in magnitude, from the lateral to mesial sides of the enamel layer, whereas only minor variations in tilt angle were found relative to enamel thickness at given locations across the enamel layer. The decussation angle between alternating rows of rod profiles within the inner enamel layer was fairly constant from the lateral to central labial sides of the enamel layer, but it increased dramatically in the mesial region of the enamel layer. The packing density of all rod profiles decreased from lateral to central labial regions of the enamel layer and then in progressing mesially, decreased slightly (inner enamel, mesial tilt), increased slightly (outer enamel layer) or almost doubled in magnitude (inner enamel, lateral tilt). It was concluded that these variations in rod tilt angle and packing densities are adaptations that allow the tooth to maintain a sharp incisal edge and shovel-shape as renewing segments formed by around 7200 ameloblasts are brought onto the occluding surface of the tooth by continuous renewal.
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Affiliation(s)
- Charles E. Smith
- Department of Biologic and Materials SciencesUniversity of Michigan School of DentistryAnn ArborMIUSA
- Department of Anatomy & Cell BiologyFaculty of MedicineMcGill UniversityMontrealQCCanada
| | - Yuanyuan Hu
- Department of Biologic and Materials SciencesUniversity of Michigan School of DentistryAnn ArborMIUSA
| | - Jan C‐C. Hu
- Department of Biologic and Materials SciencesUniversity of Michigan School of DentistryAnn ArborMIUSA
| | - James P. Simmer
- Department of Biologic and Materials SciencesUniversity of Michigan School of DentistryAnn ArborMIUSA
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28
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Yamakoshi Y, Simmer JP. Structural features, processing mechanism and gene splice variants of dentin sialophosphoprotein. Jpn Dent Sci Rev 2018; 54:183-196. [PMID: 30302137 PMCID: PMC6175968 DOI: 10.1016/j.jdsr.2018.03.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Revised: 02/12/2018] [Accepted: 03/22/2018] [Indexed: 12/03/2022] Open
Abstract
Dentin sialophosphoprotein (DSPP) plays an important role in the formation of dentin. Understanding its structure and function would provide important insights into the regulation of dentin mineralization. For the past 15 years, we have been studying DSPP-derived proteins isolated from pig dentin. Porcine DSPP is synthesized and secreted by odontoblasts and processed into three proteins, i.e., dentin sialoprotein (DSP), dentin glycoprotein (DGP), and dentin phosphoprotein (DPP), by bone morphogenetic protein 1 and matrix metalloproteinase-20 and -2. DSP is a proteoglycan that forms covalent dimers, DGP is a phosphorylated glycoprotein, and DPP is a highly phosphorylated intrinsically disordered protein with genetic polymorphisms. Furthermore, DPP is not detected in dental pulp. This is possibly due to the existence of two mRNA variants of the DSPP gene: one that encodes the DSP region alone and another that encodes full-length DSPP. The mRNA variant encoding DSP alone is expressed in dental pulp and odontoblasts, but the variant encoding full-length DSPP is predominantly expressed in odontoblasts and barely in dental pulp.
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Affiliation(s)
- Yasuo Yamakoshi
- Department of Biochemistry and Molecular Biology, School of Dental Medicine, Tsurumi University, 2-1-3 Tsurumi, Tsurumi-ku, Yokohama 230-8501, Japan
| | - James P. Simmer
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1210 Eisenhower Place, Ann Arbor, 48103, USA
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Abstract
Enamel formation requires consecutive stages of development to achieve its characteristic extreme mineral hardness. Mineralization depends on the initial presence then removal of degraded enamel proteins from the matrix via endocytosis. The ameloblast membrane resides at the interface between matrix and cell. Enamel formation is controlled by ameloblasts that produce enamel in stages to build the enamel layer (secretory stage) and to reach final mineralization (maturation stage). Each stage has specific functional requirements for the ameloblasts. Ameloblasts adopt different cell morphologies during each stage. Protein trafficking including the secretion and endocytosis of enamel proteins is a fundamental task in ameloblasts. The sites of internalization of enamel proteins on the ameloblast membrane are specific for every stage. In this review, an overview of endocytosis and trafficking of vesicles in ameloblasts is presented. The pathways for internalization and routing of vesicles are described. Endocytosis is proposed as a mechanism to remove debris of degraded enamel protein and to obtain feedback from the matrix on the status of the maturing enamel.
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Affiliation(s)
- Cong-Dat Pham
- Department of Periodontics, School of Dentistry, University of Texas Health Science Center at San AntonioSan Antonio, TX, United States
| | - Charles E. Smith
- Department of Anatomy and Cell Biology, McGill UniversityMontreal, QC, Canada
- Department of Biologic and Materials Sciences, University of MichiganAnn Arbor, MI, United States
| | - Yuanyuan Hu
- Department of Biologic and Materials Sciences, University of MichiganAnn Arbor, MI, United States
| | - Jan C-C. Hu
- Department of Biologic and Materials Sciences, University of MichiganAnn Arbor, MI, United States
| | - James P. Simmer
- Department of Biologic and Materials Sciences, University of MichiganAnn Arbor, MI, United States
| | - Yong-Hee P. Chun
- Department of Periodontics, School of Dentistry, University of Texas Health Science Center at San AntonioSan Antonio, TX, United States
- Department of Cell Systems & Anatomy, School of Medicine, University of Texas Health Science Center at San AntonioSan Antonio, TX, United States
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30
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Yamazaki H, Beniash E, Yamakoshi Y, Simmer JP, Margolis HC. Protein Phosphorylation and Mineral Binding Affect the Secondary Structure of the Leucine-Rich Amelogenin Peptide. Front Physiol 2017; 8:450. [PMID: 28706493 PMCID: PMC5489624 DOI: 10.3389/fphys.2017.00450] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2017] [Accepted: 06/14/2017] [Indexed: 12/31/2022] Open
Abstract
Previously, we have shown that serine-16 phosphorylation in native full-length porcine amelogenin (P173) and the Leucine-Rich Amelogenin Peptide (LRAP(+P)), an alternative amelogenin splice product, affects protein assembly and mineralization in vitro. Notably, P173 and LRAP(+P) stabilize amorphous calcium phosphate (ACP) and inhibit hydroxyapatite (HA) formation, while non-phosphorylated counterparts (rP172, LRAP(-P)) guide the growth of ordered bundles of HA crystals. Based on these findings, we hypothesize that the phosphorylation of full-length amelogenin and LRAP induces conformational changes that critically affect its capacity to interact with forming calcium phosphate mineral phases. To test this hypothesis, we have utilized Fourier transform infrared spectroscopy (FTIR) to determine the secondary structure of LRAP(-P) and LRAP(+P) in the absence/presence of calcium and selected mineral phases relevant to amelogenesis; i.e., hydroxyapatite (HA: an enamel crystal prototype) and (ACP: an enamel crystal precursor phase). Aqueous solutions of LRAP(-P) or LRAP(+P) were prepared with or without 7.5 mM of CaCl2 at pH 7.4. FTIR spectra of each solution were obtained using attenuated total reflectance, and amide-I peaks were analyzed to provide secondary structure information. Secondary structures of LRAP(+P) and LRAP(-P) were similarly assessed following incubation with suspensions of HA and pyrophosphate-stabilized ACP. Amide I spectra of LRAP(-P) and LRAP(+P) were found to be distinct from each other in all cases. Spectra analyses showed that LRAP(-P) is comprised mostly of random coil and β-sheet, while LRAP(+P) exhibits more β-sheet and α-helix with little random coil. With added Ca, the random coil content increased in LRAP(-P), while LRAP(+P) exhibited a decrease in α-helix components. Incubation of LRAP(-P) with HA or ACP resulted in comparable increases in β-sheet structure. Notably, however, LRAP(+P) secondary structure was more affected by ACP, primarily showing an increase in β-sheet structure, compared to that observed with added HA. These collective findings indicate that phosphorylation induces unique secondary structural changes that may enhance the functional capacity of native phosphorylated amelogenins like LRAP to stabilize an ACP precursor phase during early stages of enamel mineral formation.
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Affiliation(s)
- Hajime Yamazaki
- Center for Biomineralization, The Forsyth InstituteCambridge, MA, United States.,Department of Developmental Biology, Harvard School of Dental MedicineBoston, MA, United States
| | - Elia Beniash
- Department of Oral Biology, Center for Craniofacial Regeneration, McGowan Institute for Regenerative Medicine, University of PittsburghPittsburgh, PA, United States
| | - Yasuo Yamakoshi
- Department of Biochemistry and Molecular Biology, School of Dental Medicine, Tsurumi UniversityYokohama, Japan
| | - James P Simmer
- Department of Biologic and Materials Sciences, University of Michigan School of DentistryAnn Arbor, MI, United States
| | - Henry C Margolis
- Center for Biomineralization, The Forsyth InstituteCambridge, MA, United States.,Department of Developmental Biology, Harvard School of Dental MedicineBoston, MA, United States
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31
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Kim YJ, Kang J, Seymen F, Koruyucu M, Gencay K, Shin TJ, Hyun HK, Lee ZH, Hu JCC, Simmer JP, Kim JW. Analyses of MMP20 Missense Mutations in Two Families with Hypomaturation Amelogenesis Imperfecta. Front Physiol 2017; 8:229. [PMID: 28473773 PMCID: PMC5397402 DOI: 10.3389/fphys.2017.00229] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Accepted: 03/31/2017] [Indexed: 11/25/2022] Open
Abstract
Amelogenesis imperfecta is a group of rare inherited disorders that affect tooth enamel formation, quantitatively and/or qualitatively. The aim of this study was to identify the genetic etiologies of two families presenting with hypomaturation amelogenesis imperfecta. DNA was isolated from peripheral blood samples obtained from participating family members. Whole exome sequencing was performed using DNA samples from the two probands. Sequencing data was aligned to the NCBI human reference genome (NCBI build 37.2, hg19) and sequence variations were annotated with the dbSNP build 138. Mutations in MMP20 were identified in both probands. A homozygous missense mutation (c.678T>A; p.His226Gln) was identified in the consanguineous Family 1. Compound heterozygous MMP20 mutations (c.540T>A, p.Tyr180* and c.389C>T, p.Thr130Ile) were identified in the non-consanguineous Family 2. Affected persons in Family 1 showed hypomaturation AI with dark brown discoloration, which is similar to the clinical phenotype in a previous report with the same mutation. However, the dentition of the Family 2 proband exhibited slight yellowish discoloration with reduced transparency. Functional analysis showed that the p.Thr130Ile mutant protein had reduced activity of MMP20, while there was no functional MMP20 in the Family 1 proband. These results expand the mutational spectrum of the MMP20 and broaden our understanding of genotype-phenotype correlations in amelogenesis imperfecta.
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Affiliation(s)
- Youn Jung Kim
- Department of Molecular Genetics and Dental Research Institute, School of Dentistry, Seoul National UniversitySeoul, Korea
| | - Jenny Kang
- Department of Pediatric Dentistry and Dental Research Institute, School of Dentistry, Seoul National UniversitySeoul, Korea
| | - Figen Seymen
- Faculty of Dentistry, Department of Pedodontics, Istanbul UniversityIstanbul, Turkey
| | - Mine Koruyucu
- Faculty of Dentistry, Department of Pedodontics, Istanbul UniversityIstanbul, Turkey
| | - Koray Gencay
- Faculty of Dentistry, Department of Pedodontics, Istanbul UniversityIstanbul, Turkey
| | - Teo Jeon Shin
- Department of Pediatric Dentistry and Dental Research Institute, School of Dentistry, Seoul National UniversitySeoul, Korea
| | - Hong-Keun Hyun
- Department of Pediatric Dentistry and Dental Research Institute, School of Dentistry, Seoul National UniversitySeoul, Korea
| | - Zang Hee Lee
- Department of Cell and Developmental Biology and Dental Research Institute, School of Dentistry, Seoul National UniversitySeoul, Korea
| | - Jan C-C Hu
- Department of Biologic and Materials Sciences, University of Michigan School of DentistryAnn Arbor, MI, USA
| | - James P Simmer
- Department of Biologic and Materials Sciences, University of Michigan School of DentistryAnn Arbor, MI, USA
| | - Jung-Wook Kim
- Department of Molecular Genetics and Dental Research Institute, School of Dentistry, Seoul National UniversitySeoul, Korea.,Department of Pediatric Dentistry and Dental Research Institute, School of Dentistry, Seoul National UniversitySeoul, Korea
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Abstract
We report here a novel biomimetic approach to the regeneration of human enamel. The approach combines the use of inorganic pyrophosphate (PPi) to control the onset and rate of enamel regeneration and the use of leucine-rich amelogenin peptide (LRAP), a nonphosphorylated 56-amino acid alternative splice product of amelogenin, to regulate the shape and orientation of growing enamel crystals. This study builds on our previous findings that show LRAP can effectively guide the formation of ordered arrays of needle-like hydroxyapatite (HA) crystals in vitro and on the known role mineralization inhibitors, like PPi, play in the regulation of mineralized tissue formation. Acid-etched enamel surfaces of extracted human molars, cut perpendicular or parallel to the direction of the enamel rods, were exposed to a PPi-stabilized supersaturated calcium phosphate (CaP) solution containing 0 to 0.06 mg/mL LRAP for 20 h. In the absence of LRAP, PPi inhibition was reversed by the presence of etched enamel surfaces and led to the formation of large, randomly distributed plate-like HA crystals that were weakly attached, regardless of rod orientation. In the presence of 0.04 mg/mL LRAP, however, densely packed mineral layers, comprising bundles of small needle-like HA crystals, formed on etched surfaces that were cut perpendicular to the enamel rods. These crystals were strongly attached, and their arrangement reflected to a significant degree the underlying enamel prism pattern. In contrast, under the same conditions with LRAP, little to no crystal formation was found on enamel surfaces that were cut parallel to the direction of the enamel rods. These results suggest that LRAP preferentially interacts with ab surfaces of mature enamel crystals, inhibiting their directional growth, thus selectively promoting linear growth along the c-axis of enamel crystals. The present findings demonstrate a potential for the development of a new approach to regenerate enamel structure and properties.
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Affiliation(s)
- S Y Kwak
- 1 Center for Biomineralization, Department of Applied Oral Sciences, The Forsyth Institute, Cambridge, MA, USA
- 2 Department of Developmental Biology, Harvard School of Dental Medicine, Boston, MA, USA
| | - A Litman
- 1 Center for Biomineralization, Department of Applied Oral Sciences, The Forsyth Institute, Cambridge, MA, USA
| | - H C Margolis
- 1 Center for Biomineralization, Department of Applied Oral Sciences, The Forsyth Institute, Cambridge, MA, USA
- 2 Department of Developmental Biology, Harvard School of Dental Medicine, Boston, MA, USA
| | - Y Yamakoshi
- 3 Department of Biochemistry and Molecular Biology, School of Dental Medicine, Tsurumi University, Yokohama, Japan
| | - J P Simmer
- 4 Department of Biologic and Materials Science, University of Michigan School of Dentistry, Ann Arbor, MI, USA
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Ikawa T, Kakegawa A, Nagano T, Ando H, Yamakoshi Y, Tanabe T, Simmer JP, Hu CC, Fukae M, Oida S. Porcine Amelogenin is Expressed from the X and Y Chromosomes. J Dent Res 2016; 84:144-8. [PMID: 15668331 DOI: 10.1177/154405910508400207] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Amelogenin is the major enamel matrix component in developing teeth. In eutherian mammals, amelogenin is expressed from the X chromosome only, or from both the X and Y chromosomes. Two classes of porcine amelogenin cDNA clones have been characterized, but the chromosomal localization of the gene(s) encoding them is unknown. To determine if there are sex-based differences in the expression of porcine amelogenin, we paired PCR primers for exons 1a, 1b, 7a, and 7b, and amplified enamel organ-derived cDNA separately from porcine males and females. The results show that exons 1a/2a and 7a are always together and can be amplified from both males (XY) and females (XX). Exons 1b/2b and 7b are also always paired, but can be amplified only from females. We conclude that porcine amelogenin is expressed from separate genes on the X and Y chromosomes, and not, as previously proposed, from a single gene with two promoters.
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Affiliation(s)
- T Ikawa
- Department of Biochemistry, School of Dental Medicine, Tsurumi University, 2-1-3 Tsurumi, Tsurumi-ku, Yokohama, 230-8501, Japan
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Abstract
By the Shields classification, articulated over 30 years ago, inherited dentin defects are divided into 5 types: 3 types of dentinogenesis imperfecta (DGI), and 2 types of dentin dysplasia (DD). DGI type I is osteogenesis imperfecta (OI) with DGI. OI with DGI is caused, in most cases, by mutations in the 2 genes encoding type I collagen. Many genes are required to generate the enzymes that catalyze collagen’s diverse post-translational modifications and its assembly into fibers, fibrils, bundles, and networks. Rare inherited diseases of bone are caused by defects in these genes, and some are occasionally found to include DGI as a feature. Appreciation of the complicated genetic etiology of DGI associated with bony defects splintered the DGI type I description into a multitude of more precisely defined entities, all with their own designations. In contrast, DD-II, DGI-II, and DGI-III, each with its own pattern of inherited defects limited to the dentition, have been found to be caused by various defects in DSPP (dentin sialophosphoprotein), a gene encoding the major non-collagenous proteins of dentin. Only DD-I, an exceedingly rare condition featuring short, blunt roots with obliterated pulp chambers, remains untouched by the revolution in genetics, and its etiology is still a mystery. A major surprise in the characterization of genes underlying inherited dentin defects is the apparent lack of roles played by the genes encoding the less-abundant non-collagenous proteins in dentin, such as dentin matrix protein 1 ( DMP1), integrin-binding sialoprotein ( IBSP), matrix extracellular phosphoglycoprotein ( MEPE), and secreted phosphoprotein-1, or osteopontin ( SPP1, OPN). This review discusses the development of the dentin extracellular matrix in the context of its evolution, and discusses the phenotypes and clinical classifications of isolated hereditary defects of tooth dentin in the context of recent genetic data respecting their genetic etiologies.
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Affiliation(s)
- J-W Kim
- Seoul National University, School of Dentistry Department of Pediatric Dentistry & Dental Research Institute, 28-2 Yongon-dong, Chongno-gu, Seoul, Korea 110-749
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Seymen F, Kim YJ, Lee YJ, Kang J, Kim TH, Choi H, Koruyucu M, Kasimoglu Y, Tuna EB, Gencay K, Shin TJ, Hyun HK, Kim YJ, Lee SH, Lee ZH, Zhang H, Hu JCC, Simmer JP, Cho ES, Kim JW. Recessive Mutations in ACPT, Encoding Testicular Acid Phosphatase, Cause Hypoplastic Amelogenesis Imperfecta. Am J Hum Genet 2016; 99:1199-1205. [PMID: 27843125 PMCID: PMC5097978 DOI: 10.1016/j.ajhg.2016.09.018] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2016] [Accepted: 09/26/2016] [Indexed: 11/25/2022] Open
Abstract
Amelogenesis imperfecta (AI) is a heterogeneous group of genetic disorders affecting tooth enamel. The affected enamel can be hypoplastic and/or hypomineralized. In this study, we identified ACPT (testicular acid phosphatase) biallelic mutations causing non-syndromic, generalized hypoplastic autosomal-recessive amelogenesis imperfecta (AI) in individuals from six apparently unrelated Turkish families. Families 1, 4, and 5 were affected by the homozygous ACPT mutation c.713C>T (p.Ser238Leu), family 2 by the homozygous ACPT mutation c.331C>T (p.Arg111Cys), family 3 by the homozygous ACPT mutation c.226C>T (p.Arg76Cys), and family 6 by the compound heterozygous ACPT mutations c.382G>C (p.Ala128Pro) and 397G>A (p.Glu133Lys). Analysis of the ACPT crystal structure suggests that these mutations damaged the activity of ACPT by altering the sizes and charges of key amino acid side chains, limiting accessibility of the catalytic core, and interfering with homodimerization. Immunohistochemical analysis confirmed localization of ACPT in secretory-stage ameloblasts. The study results provide evidence for the crucial function of ACPT during amelogenesis.
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Smith CE, Hu Y, Hu JCC, Simmer JP. Ultrastructure of early amelogenesis in wild-type, Amelx-/-, and Enam-/- mice: enamel ribbon initiation on dentin mineral and ribbon orientation by ameloblasts. Mol Genet Genomic Med 2016; 4:662-683. [PMID: 27896288 PMCID: PMC5118210 DOI: 10.1002/mgg3.253] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Revised: 09/02/2016] [Accepted: 09/13/2016] [Indexed: 01/23/2023] Open
Abstract
INTRODUCTION Dental enamel is comprised of highly organized, oriented apatite crystals, but how they form is unclear. METHODS We used focused ion beam (FIB) scanning electron microscopy (SEM) to investigate early enamel formation in 7-week-old incisors from wild-type, Amelx-/-, and Enam-/- C56BL/6 mice. FIB surface imaging scans thicker samples so that the thin enamel ribbons do not pass as readily out of the plane of section, and generates serial images by a mill and view approach for computerized tomography. RESULTS We demonstrate that wild-type enamel ribbons initiate on dentin mineral on the sides and tips of mineralized collagen fibers, and extend in clusters from dentin to the ameloblast membrane. The clustering suggested that groups of enamel ribbons were initiated and then extended by finger-like membrane processes as they retracted back into the ameloblast distal membrane. These findings support the conclusions that no organic nucleator is necessary for enamel ribbon initiation (although no ribbons form in the Enam-/- mice), and that enamel ribbons elongate along the ameloblast membrane and orient in the direction of its retrograde movement. Tomographic reconstruction videos revealed a complex of ameloblast membrane processes and invaginations associated with intercellular junctions proximal to the mineralization front and also highlighted interproximal extracellular enamel matrix accumulations proximal to the interrod growth sites, which we propose are important for expanding the interrod matrix and extending interrod enamel ribbons. Amelx-/- mice produce oriented enamel ribbons, but the ribbons fuse into fan-like structures. The matrix does not expand sufficiently to support formation of the Tomes process or establish rod and interrod organization. CONCLUSION Amelogenin does not directly nucleate, shape, or orient enamel ribbons, but separates and supports the enamel ribbons, and expands the enamel matrix to accommodate continued ribbon elongation, retrograde ameloblast movement, and rod/interrod organization.
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Affiliation(s)
- Charles E Smith
- Department of Biologic and Materials SciencesUniversity of Michigan School of Dentistry1210 Eisenhower PlaceAnn ArborMichigan48108; Facility for Electron Microscopy ResearchDepartment of Anatomy and Cell BiologyFaculty of DentistryMcGill UniversityMontrealQuebecH3A 0C7Canada
| | - Yuanyuan Hu
- Department of Biologic and Materials Sciences University of Michigan School of Dentistry 1210 Eisenhower Place Ann Arbor Michigan 48108
| | - Jan C-C Hu
- Department of Biologic and Materials Sciences University of Michigan School of Dentistry 1210 Eisenhower Place Ann Arbor Michigan 48108
| | - James P Simmer
- Department of Biologic and Materials Sciences University of Michigan School of Dentistry 1210 Eisenhower Place Ann Arbor Michigan 48108
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Parry DA, Smith CE, El-Sayed W, Poulter JA, Shore RC, Logan CV, Mogi C, Sato K, Okajima F, Harada A, Zhang H, Koruyucu M, Seymen F, Hu JCC, Simmer JP, Ahmed M, Jafri H, Johnson CA, Inglehearn CF, Mighell AJ. Mutations in the pH-Sensing G-protein-Coupled Receptor GPR68 Cause Amelogenesis Imperfecta. Am J Hum Genet 2016; 99:984-990. [PMID: 27693231 PMCID: PMC5065684 DOI: 10.1016/j.ajhg.2016.08.020] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Accepted: 08/17/2016] [Indexed: 01/11/2023] Open
Abstract
Amelogenesis is the process of dental enamel formation, leading to the deposition of the hardest tissue in the human body. This process requires the intricate regulation of ion transport and controlled changes to the pH of the developing enamel matrix. The means by which the enamel organ regulates pH during amelogenesis is largely unknown. We identified rare homozygous variants in GPR68 in three families with amelogenesis imperfecta, a genetically and phenotypically heterogeneous group of inherited conditions associated with abnormal enamel formation. Each of these homozygous variants (a large in-frame deletion, a frameshift deletion, and a missense variant) were predicted to result in loss of function. GPR68 encodes a proton-sensing G-protein-coupled receptor with sensitivity in the pH range that occurs in the developing enamel matrix during amelogenesis. Immunohistochemistry of rat mandibles confirmed localization of GPR68 in the enamel organ at all stages of amelogenesis. Our data identify a role for GPR68 as a proton sensor that is required for proper enamel formation.
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Hu Y, Smith CE, Cai Z, Donnelly LAJ, Yang J, Hu JCC, Simmer JP. Enamel ribbons, surface nodules, and octacalcium phosphate in C57BL/6 Amelx-/- mice and Amelx+/- lyonization. Mol Genet Genomic Med 2016; 4:641-661. [PMID: 27896287 PMCID: PMC5118209 DOI: 10.1002/mgg3.252] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Revised: 09/07/2016] [Accepted: 09/13/2016] [Indexed: 01/05/2023] Open
Abstract
BACKGROUND Amelogenin is required for normal enamel formation and is the most abundant protein in developing enamel. METHODS Amelx+/+, Amelx+/- , and Amelx-/- molars and incisors from C57BL/6 mice were characterized using RT-PCR, Western blotting, dissecting and light microscopy, immunohistochemistry (IHC), transmission electron microscopy (TEM), scanning electron microscopy (SEM), backscattered SEM (bSEM), nanohardness testing, and X-ray diffraction. RESULTS No amelogenin protein was detected by Western blot analyses of enamel extracts from Amelx-/- mice. Amelx-/- incisor enamel averaged 20.3 ± 3.3 μm in thickness, or only 1/6th that of the wild type (122.3 ± 7.9 μm). Amelx-/- incisor enamel nanohardness was 1.6 Gpa, less than half that of wild-type enamel (3.6 Gpa). Amelx+/- incisors and molars showed vertical banding patterns unique to each tooth. IHC detected no amelogenin in Amelx-/- enamel and varied levels of amelogenin in Amelx+/- incisors, which correlated positively with enamel thickness, strongly supporting lyonization as the cause of the variations in enamel thickness. TEM analyses showed characteristic mineral ribbons in Amelx+/+ and Amelx-/- enamel extending from mineralized dentin collagen to the ameloblast. The Amelx-/- enamel ribbons were not well separated by matrix and appeared to fuse together, forming plates. X-ray diffraction determined that the predominant mineral in Amelx-/- enamel is octacalcium phosphate (not calcium hydroxyapatite). Amelx-/- ameloblasts were similar to wild-type ameloblasts except no Tomes' processes extended into the thin enamel. Amelx-/- and Amelx+/- molars both showed calcified nodules on their occlusal surfaces. Histology of D5 and D11 developing molars showed nodules forming during the maturation stage. CONCLUSION Amelogenin forms a resorbable matrix that separates and supports, but does not shape early secretory-stage enamel ribbons. Amelogenin may facilitate the conversion of enamel ribbons into hydroxyapatite by inhibiting the formation of octacalcium phosphate. Amelogenin is necessary for thickening the enamel layer, which helps maintain ribbon organization and development and maintenance of the Tomes' process.
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Affiliation(s)
- Yuanyuan Hu
- Department of Biologic and Materials Sciences University of Michigan School of Dentistry 1210 Eisenhower Place Ann Arbor Michigan 48108
| | - Charles E Smith
- Department of Biologic and Materials SciencesUniversity of Michigan School of Dentistry1210Eisenhower PlaceAnn ArborMichigan48108; Facility for Electron Microscopy ResearchDepartment of Anatomy and Cell BiologyFaculty of DentistryMcGill UniversityMontrealQuebecH3A 2B2Canada
| | - Zhonghou Cai
- Advanced Photon Source Argonne National Laboratory 9700 S. Cass Ave Building 431-B005 Argonne Illinois 60439
| | - Lorenza A-J Donnelly
- Department of Biologic and Materials Sciences University of Michigan School of Dentistry 1210 Eisenhower Place Ann Arbor Michigan 48108
| | - Jie Yang
- Department of Biologic and Materials SciencesUniversity of Michigan School of Dentistry1210Eisenhower PlaceAnn ArborMichigan48108; Department of Pediatric DentistrySchool and Hospital of StomatologyPeking University22 South AvenueZhongguancun Haidian DistrictBeijing100081China
| | - Jan C-C Hu
- Department of Biologic and Materials Sciences University of Michigan School of Dentistry 1210 Eisenhower Place Ann Arbor Michigan 48108
| | - James P Simmer
- Department of Biologic and Materials Sciences University of Michigan School of Dentistry 1210 Eisenhower Place Ann Arbor Michigan 48108
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Abstract
Recent studies have shown that native phosphorylated full-length porcine amelogenin (P173) and its predominant cleavage product (P148) can inhibit spontaneous calcium phosphate formation in vitro by stabilizing an amorphous calcium phosphate (ACP) precursor phase. Since full-length amelogenin undergoes proteolysis by matrix metalloproteinase 20 (MMP20, enamelysin) soon after secretion, the present study was conducted to assess the effect of amelogenin proteolysis on calcium phosphate formation. Calcium and phosphate were sequentially added to protein solutions without and with added MMP20 (ratio = 200:1) under physiological-like conditions of ionic strength (163 mM) in 50 mM Tris-HCl (pH 7.4) at 37 °C. Protein degradation with time was assessed by gel-electrophoresis, and mineral products formed were characterized by transmission electron microscopy (TEM). MMP20 was found to cleave P173 to primarily generate P148, along with P162, P46-148, and P63/64-148. In sharp contrast, MMP20 did not cleave P148. In addition, the formation of well-aligned bundles of enamel-like hydroxyapatite (HA) crystals was promoted in the presence of P173 with added MMP20, while only ACP particles were seen in the absence of MMP20. Although P148 was found to have a somewhat lower capacity to stabilize ACP and prevent HA formation compared with P173 in the absence of MMP20, essentially no HA formation was observed in the presence of somewhat higher concentrations of P148 regardless of MMP20 addition, due to the lack of observed protein proteolysis. Present findings suggest that ACP transformation to ordered arrays of enamel crystals may be regulated in part by the proteolysis of full-length native amelogenin, while the predominant amelogenin degradation product in developing enamel (e.g., P148) primarily serves to prevent uncontrolled mineral formation during the secretory stage of amelogenesis.
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Affiliation(s)
- S Y Kwak
- Center for Biomineralization, Department of Applied Oral Sciences, The Forsyth Institute, Cambridge, MA, USA.,Department of Developmental Biology, Harvard School of Dental Medicine, Boston, MA, USA
| | - Y Yamakoshi
- Department of Biochemistry and Molecular Biology, School of Dental Medicine, Tsurumi University, Yokohama, Japan
| | - J P Simmer
- Department of Biologic and Materials Science, University of Michigan School of Dentistry, Ann Arbor, MI, USA
| | - H C Margolis
- Center for Biomineralization, Department of Applied Oral Sciences, The Forsyth Institute, Cambridge, MA, USA .,Department of Developmental Biology, Harvard School of Dental Medicine, Boston, MA, USA
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Yang J, Kawasaki K, Lee M, Reid BM, Nunez SM, Choi M, Seymen F, Koruyucu M, Kasimoglu Y, Estrella-Yuson N, Lin BPJ, Simmer JP, Hu JCC. The dentin phosphoprotein repeat region and inherited defects of dentin. Mol Genet Genomic Med 2016; 4:28-38. [PMID: 26788535 PMCID: PMC4707025 DOI: 10.1002/mgg3.176] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Revised: 08/05/2015] [Accepted: 08/06/2015] [Indexed: 11/12/2022] Open
Abstract
Nonsyndromic dentin defects classified as type II dentin dysplasia and types II and III dentinogenesis imperfecta are caused by mutations in DSPP (dentin sialophosphoprotein). Most reported disease‐causing DSPP mutations occur within the repetitive DPP (dentin phosphoprotein) coding sequence. We characterized the DPP sequences of five probands with inherited dentin defects using single molecule real‐time (SMRT) DNA sequencing. Eight of the 10 sequences matched previously reported DPP length haplotypes and two were novel. Alignment with known DPP sequences showed 32 indels arranged in 36 different patterns. Sixteen of the 32 indels were not represented in more than one haplotype. The 25 haplotypes with confirmed indels were aligned to generate a tree that describes how the length variations might have evolved. Some indels were independently generated in multiple lines. A previously reported disease‐causing DSPP mutation in Family 1 was confirmed and its position clarified (c.3135delC; p.Ser1045Argfs*269). A novel frameshift mutation (c.3504_3508dup; p.Asp1170Alafs*146) caused the dentin defects in Family 2. A COL1A2 (c.2027G>A or p.Gly676Asp) missense mutation, discovered by whole‐exome sequencing, caused the dentin defects in Family 3. We conclude that SMRT sequencing characterizes the DPP repeat region without cloning and can improve our understanding of normal and pathological length variations in DSPP alleles.
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Affiliation(s)
- Jie Yang
- Department of Biologic and Materials SciencesUniversity of Michigan School of Dentistry1210 Eisenhower PlaceAnn ArborMichigan; Department of Pediatric DentistrySchool and Hospital of StomatologyPeking University22 South AvenueZhongguancun Haidian DistrictBeijing100081China
| | - Kazuhiko Kawasaki
- Department of Anthropology Pennsylvania State University University Park Pennsylvania 16802
| | - Moses Lee
- Department of Biomedical Sciences Seoul National University College of Medicine 275-1 Yongon-dong, Chongno-gu Seoul 110-768 Korea
| | - Bryan M Reid
- Department of Biologic and Materials Sciences University of Michigan School of Dentistry 1210 Eisenhower Place Ann Arbor Michigan
| | - Stephanie M Nunez
- Department of Biologic and Materials Sciences University of Michigan School of Dentistry 1210 Eisenhower Place Ann Arbor Michigan
| | - Murim Choi
- Department of Biomedical Sciences Seoul National University College of Medicine 275-1 Yongon-dong, Chongno-gu Seoul 110-768 Korea
| | - Figen Seymen
- Department of Pedodontics Faculty of Dentistry Istanbul University Istanbul Turkey
| | - Mine Koruyucu
- Department of Pedodontics Faculty of Dentistry Istanbul University Istanbul Turkey
| | - Yelda Kasimoglu
- Department of Pedodontics Faculty of Dentistry Istanbul University Istanbul Turkey
| | - Ninna Estrella-Yuson
- Department of Paediatric Dentistry Women's and Children's Hospital 72 King William Road North Adelaide South Australia 5006 Australia
| | - Brent P J Lin
- Department of Pediatric Dentistry School of Dentistry University of California San Francisco California
| | - James P Simmer
- Department of Biologic and Materials Sciences University of Michigan School of Dentistry 1210 Eisenhower Place Ann Arbor Michigan
| | - Jan C-C Hu
- Department of Biologic and Materials Sciences University of Michigan School of Dentistry 1210 Eisenhower Place Ann Arbor Michigan
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Hu Y, Smith CE, Richardson AS, Bartlett JD, Hu JCC, Simmer JP. MMP20, KLK4, and MMP20/KLK4 double null mice define roles for matrix proteases during dental enamel formation. Mol Genet Genomic Med 2015; 4:178-96. [PMID: 27066511 PMCID: PMC4799876 DOI: 10.1002/mgg3.194] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Revised: 11/12/2015] [Accepted: 11/13/2015] [Indexed: 01/08/2023] Open
Abstract
Matrix metalloproteinase 20 (MMP20) and kallikrein‐related peptidase 4 (KLK4) are secreted proteinases that are essential for proper dental enamel formation. We characterized and compared enamel formed in wild‐type, Mmp20−/−, Klk4−/−, Mmp20+/−Klk4+/−, and Mmp20−/−Klk4−/− mice using dissecting and light microscopy, backscattered scanning electron microscopy (bSEM), SEM, microcomputed tomography (μCT), and energy‐dispersive X‐ray analysis (EDX). Following eruption, fractures were observed on Mmp20−/−, Klk4−/−, Mmp20+/−Klk4+/−, and Mmp20−/−Klk4−/− molars. Failure of the enamel in the Mmp20+/−Klk4+/− molars was unexpected and suggested that digenic effects could contribute to the etiology of amelogenesis imperfecta in humans. Micro‐CT analyses of hemimandibles demonstrated significantly reduced high‐density enamel volume in the Mmp20−/− and Klk4−/− mice relative to the wild‐type, which was further reduced in Mmp20−/−Klk4−/− mice. bSEM images of 7‐week Mmp20−/− and Mmp20−/−Klk4−/− mandibular incisors showed rough, pitted enamel surfaces with numerous indentations and protruding nodules. The Mmp20+/− and Mmp20+/−Klk4+/− incisors showed prominent, evenly spaced, horizontal ridges that were more distinct in Mmp20+/−Klk4+/− incisors relative to Mmp20+/− incisors due to the darkening of the valleys between the ridges. In cross sections, the Mmp20−/− and Mmp20−/−Klk4−/− exhibited three distinct layers. The outer layer exhibited a disturbed elemental composition and an irregular enamel surface covered with nodules. The Mmp20 null enamel was apparently unable to withstand the sheer forces associated with eruption and separated from dentin during development. Cells invaded the cracks and interposed between the dentin and enamel layers. MMP20 and KLK4 serve overlapping and complementary functions to harden enamel by removing protein, but MMP20 potentially serves multiple additional functions necessary for the adherence of enamel to dentin, the release of intercellular protein stores into the enamel matrix, the retreat of ameloblasts to facilitate thickening of the enamel layer, and the timely transition of ameloblasts to maturation.
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Affiliation(s)
- Yuanyuan Hu
- Departments of Biologic and Materials Sciences University of Michigan School of Dentistry 1210 Eisenhower Place Ann Arbor Michigan 48108
| | - Charles E Smith
- Departments of Biologic and Materials SciencesUniversity of Michigan School of Dentistry1210 Eisenhower PlaceAnn ArborMichigan48108; Facility for Electron Microscopy ResearchDepartment of Anatomy and Cell Biology and Faculty of DentistryMcGill UniversityMontrealQuebecH3A 2B2Canada
| | - Amelia S Richardson
- Departments of Biologic and Materials Sciences University of Michigan School of Dentistry 1210 Eisenhower Place Ann Arbor Michigan 48108
| | - John D Bartlett
- Office of Research College of Dentistry Ohio State University 4139 Postle Hall, 305 W. 12th Ave. Columbus Ohio 43210
| | - Jan C C Hu
- Departments of Biologic and Materials Sciences University of Michigan School of Dentistry 1210 Eisenhower Place Ann Arbor Michigan 48108
| | - James P Simmer
- Departments of Biologic and Materials Sciences University of Michigan School of Dentistry 1210 Eisenhower Place Ann Arbor Michigan 48108
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Vieira AR, Lee M, Vairo F, Loguercio Leite JC, Munerato MC, Visioli F, D'Ávila SR, Wang SK, Choi M, Simmer JP, Hu JCC. Root anomalies and dentin dysplasia in autosomal recessive hyperphosphatemic familial tumoral calcinosis (HFTC). Oral Surg Oral Med Oral Pathol Oral Radiol 2015; 120:e235-9. [PMID: 26337219 PMCID: PMC4640955 DOI: 10.1016/j.oooo.2015.05.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Revised: 04/30/2015] [Accepted: 05/11/2015] [Indexed: 01/17/2023]
Abstract
Hyperphosphatemic familial tumoral calcinosis (HFTC, OMIM #211900) is an autosomal recessive metabolic disorder characterized by hyperphosphatemia, tooth root defects, and the progressive deposition of calcium phosphate crystals in periarticular spaces, soft tissues, and sometimes bone.(1) In this HFTC case report, we document the dental phenotype associated with a homozygous missense mutation (g.29077 C>T; c.484 C>T; p.Arg162*) in GALNT3 (OMIM 6017563), a gene encoding UDP-GalNAc transferase 3 that catalyzes the first step of O-linked oligosaccharide biosynthesis in the Golgi. The medical and dental pathology is believed to be caused primarily by high serum phosphate levels (hyperphosphatemia), which, in turn, is caused by failure of GALNT3 to glycosylate the phosphate regulator protein FGF23, impairing its ability inhibit reabsorption of filtered phosphate in the kidneys.
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Affiliation(s)
- Alexandre R Vieira
- Departments of Oral Biology and Pediatric Dentistry, Center for Craniofacial and Dental Genetics, School of Dental Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA; Department of Human Genetics, Graduate School of Public Health; Clinical and Translational Science Institute, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Moses Lee
- Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul, Korea
| | - Filippo Vairo
- Medical Genetics Service, Hospital de Clínicas de Porto Alegre, RS, Brazil
| | | | - Maria Cristina Munerato
- Department of Oral Pathology, School of Dentistry, Universidade Federal do Rio Grande do Sul, RS, Brazil
| | - Fernanda Visioli
- Department of Oral Pathology, School of Dentistry, Universidade Federal do Rio Grande do Sul, RS, Brazil
| | | | - Shih-Kai Wang
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, Michigan, USA
| | - Murim Choi
- Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul, Korea.
| | - James P Simmer
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, Michigan, USA
| | - Jan C-C Hu
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, Michigan, USA
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Núñez SM, Chun YHP, Ganss B, Hu Y, Richardson AS, Schmitz JE, Fajardo R, Yang J, Hu JCC, Simmer JP. Maturation stage enamel malformations in Amtn and Klk4 null mice. Matrix Biol 2015; 52-54:219-233. [PMID: 26620968 DOI: 10.1016/j.matbio.2015.11.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2015] [Revised: 11/20/2015] [Accepted: 11/23/2015] [Indexed: 12/14/2022]
Abstract
Amelotin (AMTN) and kallikrein-4 (KLK4) are secreted proteins specialized for enamel biomineralization. We characterized enamel from wild-type, Amtn(-/-), Klk4(-/-), Amtn(+/-)Klk4(+/-) and Amtn(-/-)Klk4(-/-) mice to gain insights into AMTN and KLK4 functions during amelogenesis. All of the null mice were healthy and fertile. The mandibular incisors in Amtn(-/-), Klk4(-/-) and Amtn(-/-)Klk4(-/-) mice were chalky-white and chipped. No abnormalities except in enamel were observed, and no significant differences were detected in enamel thickness or volume, or in rod decussation. Micro-computed tomography (μCT) maximum intensity projections localized the onset of enamel maturation in wild-type incisors distal to the first molar, but mesial to this position in Amtn(-/-), Klk4(-/-) and Amtn(-/-)Klk4(-/-) mice, demonstrating a delay in enamel maturation in Amtn(-/-) incisors. Micro-CT detected significantly reduced enamel mineral density (2.5 and 2.4gHA/cm(3)) in the Klk4(-/-) and Amtn(-/-)Klk4(-/-) mice respectively, compared with wild-type enamel (3.1gHA/cm(3)). Backscatter scanning electron microscopy showed that mineral density progressively diminished with enamel depth in the Klk4(-/-) and Amtn(-/-)Klk4(-/-) mice. The Knoop hardness of the Amtn(-/-) outer enamel was significantly reduced relative to the wild-type and was not as hard as the middle or inner enamel. Klk4(-/-) enamel hardness was significantly reduced at all levels, but the outer enamel was significantly harder than the inner and middle enamel. Thus the hardness patterns of the Amtn(-/-) and Klk4(-/-) mice were distinctly different, while the Amtn(-/-)Klk4(-/-) outer enamel was not as hard as in the Amtn(-/-) and Klk4(-/-) mice. We conclude that AMTN and KLK4 function independently, but are both necessary for proper enamel maturation.
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Affiliation(s)
- Stephanie M Núñez
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1210 Eisenhower Pl., Ann Arbor, MI, USA 48108.
| | - Yong-Hee P Chun
- Department of Periodontics, School of Dentistry, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Dr., San Antonio, TX 78240, USA.
| | - Bernhard Ganss
- Matrix Dynamics Group, Faculty of Dentistry, University of Toronto, 150 College Street, Fitzgerald Building, Toronto, ON M5S 3E2, Canada.
| | - Yuanyuan Hu
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1210 Eisenhower Pl., Ann Arbor, MI, USA 48108.
| | - Amelia S Richardson
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1210 Eisenhower Pl., Ann Arbor, MI, USA 48108.
| | - James E Schmitz
- Department of Orthopaedics, RAYO, Carlisle Center for Bone and Mineral Imaging, School of Medicine, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Dr., San Antonio, TX, USA.
| | - Roberto Fajardo
- Department of Orthopaedics, RAYO, Carlisle Center for Bone and Mineral Imaging, School of Medicine, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Dr., San Antonio, TX, USA.
| | - Jie Yang
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1210 Eisenhower Pl., Ann Arbor, MI, USA 48108; Department of Pediatric Dentistry, School and Hospital of Stomatology, Peking University, 22 South Avenue, Zhongguancun Haidian District, Beijing 100081, PR China.
| | - Jan C-C Hu
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1210 Eisenhower Pl., Ann Arbor, MI, USA 48108.
| | - James P Simmer
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1210 Eisenhower Pl., Ann Arbor, MI, USA 48108.
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Wang SK, Hu Y, Yang J, Smith CE, Richardson AS, Yamakoshi Y, Lee YL, Seymen F, Koruyucu M, Gencay K, Lee M, Choi M, Kim JW, Hu JCC, Simmer JP. Fam83h null mice support a neomorphic mechanism for human ADHCAI. Mol Genet Genomic Med 2015; 4:46-67. [PMID: 26788537 PMCID: PMC4707031 DOI: 10.1002/mgg3.178] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Revised: 08/17/2015] [Accepted: 08/18/2015] [Indexed: 11/10/2022] Open
Abstract
Truncation mutations in FAM83H (family with sequence similarity 83, member H) cause autosomal dominant hypocalcified amelogenesis imperfecta (ADHCAI), but little is known about FAM83H function and the pathogenesis of ADHCAI. We recruited three ADHCAI families and identified two novel (p.Gln457*; p.Lys639*) and one previously documented (p.Q452*) disease‐causing FAM83H mutations. We generated and characterized Fam83h‐knockout/lacZ‐knockin mice. Surprisingly, enamel thickness, density, Knoop hardness, morphology, and prism patterns were similar in Fam83h+/+, Fam83h+/−, and Fam83h−/− mice. The histology of ameloblasts in all stages of development, in both molars and incisors, was virtually identical in all three genotypes and showed no signs of pathology, although the Fam83h−/− mice usually died after 2 weeks and rarely survived to 7 weeks. LacZ expression in the knockin mice was used to report Fam83h expression in the epithelial tissues of many organs, notably in skin and hair follicles, which manifested a disease phenotype. Pull‐down studies determined that FAM83H dimerizes through its N‐terminal phospholipase D‐like (PLD‐like) domain and identified potential FAM83H interacting proteins. Casein kinase 1 (CK1) interacts with the FAM83H PLD‐like domain via an F270‐X‐X‐X‐F274‐X‐X‐X‐F278 motif. CK1 can phosphorylate FAM83H in vitro, and many phosphorylation sites were identified in the FAM83H C‐terminus. Truncation of FAM83H alters its subcellular localization and that of CK1. Our results support the conclusion that FAM83H is not necessary for proper dental enamel formation in mice, but may act as a scaffold protein that localizes CK1. ADHCAI is likely caused by gain‐of‐function effects mediated by truncated FAM83H, which potentially mislocalizes CK1 as part of its pathological mechanism.
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Affiliation(s)
- Shih-Kai Wang
- Department of Biologic and Materials Sciences University of Michigan School of Dentistry 1210 Eisenhower Pl. Ann Arbor Michigan 48108
| | - Yuanyuan Hu
- Department of Biologic and Materials Sciences University of Michigan School of Dentistry 1210 Eisenhower Pl. Ann Arbor Michigan 48108
| | - Jie Yang
- Department of Biologic and Materials SciencesUniversity of Michigan School of Dentistry1210 Eisenhower Pl.Ann ArborMichigan48108; Department of Pediatric DentistrySchool and Hospital of StomatologyPeking University22 South Avenue ZhongguancunHaidian DistrictBeijing100081China
| | - Charles E Smith
- Facility for Electron Microscopy Research Department of Anatomy and Cell Biology and Faculty of Dentistry McGill University 3640 University Street Montreal Quebec H3A 2C7 Canada
| | - Amelia S Richardson
- Department of Biologic and Materials Sciences University of Michigan School of Dentistry 1210 Eisenhower Pl. Ann Arbor Michigan 48108
| | - Yasuo Yamakoshi
- Department of Biochemistry and Molecular Biology School of Dental Medicine Tsurumi University 2-1-3 Tsurumi Tsurumi-ku Yokohama 230-8501 Japan
| | - Yuan-Ling Lee
- Graduate Institute of Clinical Dentistry National Taiwan University No. 1, Chang-Te St Taipei 10048 Taiwan
| | - Figen Seymen
- Department of Pedodontics Faculty of Dentistry Istanbul University Istanbul Turkey
| | - Mine Koruyucu
- Department of Pedodontics Faculty of Dentistry Istanbul University Istanbul Turkey
| | - Koray Gencay
- Department of Pedodontics Faculty of Dentistry Istanbul University Istanbul Turkey
| | - Moses Lee
- Department of Biomedical Sciences Seoul National University College of Medicine 275-1 Yongon-dong Chongno-gu Seoul 110-768 Korea
| | - Murim Choi
- Department of Biomedical Sciences Seoul National University College of Medicine 275-1 Yongon-dong Chongno-gu Seoul 110-768 Korea
| | - Jung-Wook Kim
- Department of Pediatric Dentistry & Dental Research Institute School of Dentistry Seoul National University 275-1 Yongon-dong Chongno-gu Seoul 110-768 Korea
| | - Jan C-C Hu
- Department of Biologic and Materials Sciences University of Michigan School of Dentistry 1210 Eisenhower Pl. Ann Arbor Michigan 48108
| | - James P Simmer
- Department of Biologic and Materials Sciences University of Michigan School of Dentistry 1210 Eisenhower Pl. Ann Arbor Michigan 48108
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45
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Abstract
Kallikrein-related peptidase 4 (KLK4) is a secreted serine protease that degrades residual enamel proteins to facilitate their removal by ameloblasts, which increases mineralization and hardens the enamel. Mutations in human KLK4 cause hypomaturation amelogenesis imperfecta. Enamel formed by Klk4 null mice is normal in thickness and prism structure, but the enamel layer retains proteins, is hypomineralized, and undergoes rapid attrition following tooth eruption. We searched multiple databases, retrieved Klk4 and Klk5 from various mammalian genomes, and identified Klk4 in 46 boreoeutherian genomes. In non-Boreoeutheria, Klk4 was detected in only one afrotherian genome (as a pseudogene), and not in the other six afrotherian, two xenarthran, or three marsupial genomes. In contrast, Klk5 was detected in both marsupial and eutherian mammals. Our phylogenetic and mutation rate analyses support the hypothesis that Klk4 arose from Klk5 by gene duplication near the divergence of Afrotheria, Xenarthra and Boreoeutheria, and that functionally-differentiated Klk4 survived only in Boreoeutheria. Afrotherian mammals share the feature of delayed dental eruption relative to boreoeutherian mammals. KLK4 shortens the time required for enamel maturation and could have alleviated negative selection following mutations that resulted in thicker enamel or earlier tooth eruption, without reducing enamel hardness or causing dental attrition.
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46
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Wang SK, Hu Y, Yang J, Smith CE, Nunez SM, Richardson AS, Pal S, Samann AC, Hu JCC, Simmer JP. Critical roles for WDR72 in calcium transport and matrix protein removal during enamel maturation. Mol Genet Genomic Med 2015; 3:302-19. [PMID: 26247047 PMCID: PMC4521966 DOI: 10.1002/mgg3.143] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Revised: 03/02/2015] [Accepted: 03/02/2015] [Indexed: 12/19/2022] Open
Abstract
Defects in WDR72 (WD repeat-containing protein 72) cause autosomal recessive hypomaturation amelogenesis imperfecta. We generated and characterized Wdr72-knockout/lacZ-knockin mice to investigate the role of WDR72 in enamel formation. In all analyses, enamel formed by Wdr72 heterozygous mice was indistinguishable from wild-type enamel. Without WDR72, enamel mineral density increased early during the maturation stage but soon arrested. The null enamel layer was only a tenth as hard as wild-type enamel and underwent rapid attrition following eruption. Despite the failure to further mineralize enamel deposited during the secretory stage, ectopic mineral formed on the enamel surface and penetrated into the overlying soft tissue. While the proteins in the enamel matrix were successfully degraded, the digestion products remained inside the enamel. Interactome analysis of WDR72 protein revealed potential interactions with clathrin-associated proteins and involvement in ameloblastic endocytosis. The maturation stage mandibular incisor enamel did not stain with methyl red, indicating that the enamel did not acidify beneath ruffle-ended ameloblasts. Attachment of maturation ameloblasts to the enamel layer was weakened, and SLC24A4, a critical ameloblast calcium transporter, did not localize appropriately along the ameloblast distal membrane. Fewer blood vessels were observed in the papillary layer supporting ameloblasts. Specific WDR72 expression by maturation stage ameloblasts explained the observation that enamel thickness and rod decussation (established during the secretory stage) are normal in the Wdr72 null mice. We conclude that WDR72 serves critical functions specifically during the maturation stage of amelogenesis and is required for both protein removal and enamel mineralization.
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Affiliation(s)
- Shih-Kai Wang
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry 1210 Eisenhower Pl., Ann Arbor, Michigan, 48108
| | - Yuanyuan Hu
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry 1210 Eisenhower Pl., Ann Arbor, Michigan, 48108
| | - Jie Yang
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry 1210 Eisenhower Pl., Ann Arbor, Michigan, 48108 ; Department of Pediatric Dentistry, School and Hospital of Stomatology, Peking University 22 South Avenue Zhongguancun, Haidian District, Beijing, 100081, China
| | - Charles E Smith
- Facility for Electron Microscopy Research, Department of Anatomy and Cell Biology and Faculty of Dentistry, McGill University 3640 University Street, Montreal, Quebec, Canada, H3A 2B2
| | - Stephanie M Nunez
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry 1210 Eisenhower Pl., Ann Arbor, Michigan, 48108
| | - Amelia S Richardson
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry 1210 Eisenhower Pl., Ann Arbor, Michigan, 48108
| | - Soumya Pal
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry 1210 Eisenhower Pl., Ann Arbor, Michigan, 48108
| | - Andrew C Samann
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry 1210 Eisenhower Pl., Ann Arbor, Michigan, 48108
| | - Jan C-C Hu
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry 1210 Eisenhower Pl., Ann Arbor, Michigan, 48108
| | - James P Simmer
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry 1210 Eisenhower Pl., Ann Arbor, Michigan, 48108
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47
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Affiliation(s)
- J D Bartlett
- Department of Mineralized Tissue Biology, The Forsyth Institute, Cambridge, MA, USA
| | - J P Simmer
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, USA
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48
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Yang J, Wang SK, Choi M, Reid BM, Hu Y, Lee YL, Herzog CR, Kim-Berman H, Lee M, Benke PJ, Lloyd KCK, Simmer JP, Hu JCC. Taurodontism, variations in tooth number, and misshapened crowns in Wnt10a null mice and human kindreds. Mol Genet Genomic Med 2014; 3:40-58. [PMID: 25629078 PMCID: PMC4299714 DOI: 10.1002/mgg3.111] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2014] [Revised: 07/30/2014] [Accepted: 07/31/2014] [Indexed: 01/22/2023] Open
Abstract
WNT10A is a signaling molecule involved in tooth development, and WNT10A defects are associated with tooth agenesis. We characterized Wnt10a null mice generated by the knockout mouse project (KOMP) and six families with WNT10A mutations, including a novel p.Arg104Cys defect, in the absence of EDA,EDAR, or EDARADD variations. Wnt10a null mice exhibited supernumerary mandibular fourth molars, and smaller molars with abnormal cusp patterning and root taurodontism. Wnt10a−/− incisors showed distinctive apical–lingual wedge-shaped defects. These findings spurred us to closely examine the dental phenotypes of our WNT10A families. WNT10A heterozygotes exhibited molar root taurodontism and mild tooth agenesis (with incomplete penetrance) in their permanent dentitions. Individuals with two defective WNT10A alleles showed severe tooth agenesis and had fewer cusps on their molars. The misshapened molar crowns and roots were consistent with the Wnt10a null phenotype and were not previously associated with WNT10A defects. The missing teeth contrasted with the presence of supplemental teeth in the Wnt10a null mice and demonstrated mammalian species differences in the roles of Wnt signaling in early tooth development. We conclude that molar crown and root dysmorphologies are caused by WNT10A defects and that the severity of the tooth agenesis correlates with the number of defective WNT10A alleles.
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Affiliation(s)
- Jie Yang
- Department of Pediatric Dentistry, School and Hospital of Stomatology, Peking University 22 South Avenue Zhongguancun Haidian District, Beijing, 100081, China ; Department of Biologic and Materials Sciences, University of Michigan School of Dentistry 1210 Eisenhower Place, Ann Arbor, Michigan, 48108
| | - Shih-Kai Wang
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry 1210 Eisenhower Place, Ann Arbor, Michigan, 48108
| | - Murim Choi
- Department of Biomedical Sciences, College of Medicine, Seoul National University 275-1 Yongon-dong, Chongno-gu, Seoul, 110-768, Korea ; Department of Genetics, Howard Hughes Medical Institute, Yale University School of Medicine 333 Cedar Street, New Haven, Connecticut, 06520
| | - Bryan M Reid
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry 1210 Eisenhower Place, Ann Arbor, Michigan, 48108
| | - Yuanyuan Hu
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry 1210 Eisenhower Place, Ann Arbor, Michigan, 48108
| | - Yuan-Ling Lee
- Graduate Institute of Clinical Dentistry, National Taiwan University No. 1 Chang-Te Street, Taipei, 10048, Taiwan, China
| | - Curtis R Herzog
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry 1210 Eisenhower Place, Ann Arbor, Michigan, 48108
| | - Hera Kim-Berman
- Department of Orthodontics and Pediatric Dentistry, University of Michigan School of Dentistry, 1011 N. University Ann Arbor, Michigan, 48109-1078
| | - Moses Lee
- Department of Biomedical Sciences, College of Medicine, Seoul National University 275-1 Yongon-dong, Chongno-gu, Seoul, 110-768, Korea
| | - Paul J Benke
- Department of Medical Genetics, Joe DiMaggio Children's Hospital 1150 N. 35th Avenue, Suite 490, Hollywood, Florida, 33021
| | - K C Kent Lloyd
- Mouse Biology Program (MBP), University of California 2795 Second Street, Suite 400, Davis, California, 95618
| | - James P Simmer
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry 1210 Eisenhower Place, Ann Arbor, Michigan, 48108
| | - Jan C-C Hu
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry 1210 Eisenhower Place, Ann Arbor, Michigan, 48108
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49
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Abstract
The purpose of this study was to identify the major molecular components in the secretory and maturation stages of amelogenesis through transcriptome analyses. Ameloblasts (40 sections per age group) were laser micro-dissected from Day 5 (secretory stage) and Days 11-12 (maturation stage) first molars. PolyA+ RNA was isolated from the lysed cells, converted to cDNA, and amplified to generate a cDNA library. DNA sequences were obtained using next generation sequencing and analyzed to identify genes whose expression had increased or decreased at least 1.5-fold in maturation stage relative to secretory stage ameloblasts. Among the 9198 genes that surpassed the quality threshold, 373 showed higher expression in secretory stage, while 614 genes increased in maturation stage ameloblasts. The results were cross-checked against a previously published transcriptome generated from tissues overlying secretory and maturation stage mouse incisor enamel and 34 increasing and 26 decreasing expressers common to the two studies were identified. Expression of F2r, which encodes protease activated receptor 1 (PAR1) that showed 10-fold higher expression during the secretory stage in our transcriptome analysis, was characterized in mouse incisors by immunohistochemistry. PAR1 was detected in secretory, but not maturation stage ameloblasts. We conclude that transcriptome analyses are a good starting point for identifying genes/proteins that are critical for proper dental enamel formation and that PAR1 is specifically expressed by secretory stage ameloblasts.
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Affiliation(s)
- James P. Simmer
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, USA
| | - Amelia S. Richardson
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, USA
| | - Shih-Kai Wang
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, USA
| | - Bryan M. Reid
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, USA
| | - Yongsheng Bai
- Department of Computational Medicine and Bioinformatics, University of Michigan Medical School, Ann Arbor, MI, USA,Morgridge Institute for Research, University of Wisconsin-Madison, Madison, WI, USA
| | - Yuanyuan Hu
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, USA
| | - Jan C.-C. Hu
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, USA
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50
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Abstract
Our previous in vitro studies have shown that recombinant full-length porcine amelogenin rP172 can transiently stabilize amorphous calcium phosphate (ACP) and uniquely guide the formation of well-aligned bundles of hydroxyapatite (HA) crystals, as seen in the secretory stage of amelogenesis. This functional capacity is dependent on the hydrophilic C-terminal domain of full-length amelogenin. However, we have also found that native phosphorylated (single S-16 site) forms of full-length (P173) and C-terminal cleaved (P148) amelogenins can stabilize ACP for > 2 d and prevent HA formation. The present study was carried out to test the hypothesis that, at reduced concentrations, native full-length P173 also has the capacity to guide ordered HA formation. The effect of P148 and P173 concentrations (0.2-2.0 mg/ml) on the rate of spontaneous calcium phosphate precipitation was monitored via changes in solution pH, while mineral phases formed were assessed using TEM. At higher P173 concentrations (1.0-2.0 mg/ml), limited mineral formation occurred and only ACP nanoparticles were observed during a 48 h period. However, at 0.4 mg/ml P173, a predominance of organized bundles of linear, needle-like HA crystals were observed. At 0.2 mg/ml of P173, limited quantities of less organized HA crystals were found. Although P148 similarly stabilized ACP, it did not guide ordered HA formation, like P173. Hence, the establishment of the hierarchical enamel structure during secretory stage amelogenesis may be regulated by the partial removal of full-length amelogenin via MMP20 proteolysis, while predominant amelogenin degradation products, like P148, serve to prevent uncontrolled mineral formation.
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Affiliation(s)
- Seo-Young Kwak
- Center for Biomineralization, Department of Applied Oral Sciences, The Forsyth Institute, Cambridge, MA 02142,Department of Developmental Biology, Harvard School of Dental Medicine, Boston, MA 02115
| | - Sonia Kim
- Goldman School of Dental Medicine, Boston University, Boston, MA 02118
| | - Yasuo Yamakoshi
- Department of Biochemistry and Molecular Biology School of Dental Medicine, Tsurumi University, Yokohama, 230-8501 Japan
| | - James P. Simmer
- Department of Biologic and Materials Science, University of Michigan School of Dentistry, Ann Arbor, MI 48108
| | - Elia Beniash
- Department of Oral Biology, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | - Henry C. Margolis
- Center for Biomineralization, Department of Applied Oral Sciences, The Forsyth Institute, Cambridge, MA 02142,Department of Developmental Biology, Harvard School of Dental Medicine, Boston, MA 02115
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