1
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Yerabandi N, Kouznetsova VL, Kesari S, Tsigelny IF. The role of BAG3 in dilated cardiomyopathy and its association with Charcot-Marie-Tooth disease type 2. ACTA MYOLOGICA : MYOPATHIES AND CARDIOMYOPATHIES : OFFICIAL JOURNAL OF THE MEDITERRANEAN SOCIETY OF MYOLOGY 2022; 41:59-75. [PMID: 35832504 PMCID: PMC9237749 DOI: 10.36185/2532-1900-071] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Accepted: 06/13/2022] [Indexed: 11/03/2022]
Abstract
Bcl2-associated athanogene 3 (BAG3) is a multifunctional cochaperone responsible for protein quality control within cells. BAG3 interacts with chaperones HSPB8 and Hsp70 to transport misfolded proteins to the Microtubule Organizing Center (MTOC) and degrade them in autophagosomes in a process known as Chaperone Assisted Selective Autophagy (CASA). Mutations in the second conserved IPV motif of BAG3 are known to cause Dilated Cardiomyopathy (DCM) by inhibiting adequate removal of non-native proteins. The proline 209 to leucine (P209L) BAG3 mutant in particular causes the aggregation of BAG3 and misfolded proteins as well as the sequestration of essential chaperones. The exact mechanisms of protein aggregation in DCM are unknown. However, the similar presence of insoluble protein aggregates in Charcot-Marie-Tooth disease type 2 (CMT2) induced by the proline 182 to leucine (P182L) HSPB1 mutant points to a possible avenue for future research: IPV motif. In this review, we summarize the molecular mechanisms of CASA and the currently known pathological effects of mutated BAG3 in DCM. Additionally, we will provide insight on the importance of the IPV motif in protein aggregation by analyzing a potential association between DCM and CMT2.
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Affiliation(s)
- Nitya Yerabandi
- REHS program, San Diego Supercomputer Center, University of California, San Diego, CA, USA
| | - Valentina L. Kouznetsova
- San Diego Supercomputer Center, University of California, San Diego, CA, USA,Biana, La Jolla, CA, USA
| | | | - Igor F. Tsigelny
- Correspondence Igor F. Tsigelny Department of Neurosciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0505, USA. E-mail:
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2
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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] [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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3
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Sanese P, Fasano C, Buscemi G, Bottino C, Corbetta S, Fabini E, Silvestri V, Valentini V, Disciglio V, Forte G, Lepore Signorile M, De Marco K, Bertora S, Grossi V, Guven U, Porta N, Di Maio V, Manoni E, Giannelli G, Bartolini M, Del Rio A, Caretti G, Ottini L, Simone C. Targeting SMYD3 to Sensitize Homologous Recombination-Proficient Tumors to PARP-Mediated Synthetic Lethality. iScience 2020; 23:101604. [PMID: 33205017 PMCID: PMC7648160 DOI: 10.1016/j.isci.2020.101604] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Revised: 08/07/2020] [Accepted: 09/21/2020] [Indexed: 12/17/2022] Open
Abstract
SMYD3 is frequently overexpressed in a wide variety of cancers. Indeed, its inactivation reduces tumor growth in preclinical in vivo animal models. However, extensive characterization in vitro failed to clarify SMYD3 function in cancer cells, although confirming its importance in carcinogenesis. Taking advantage of a SMYD3 mutant variant identified in a high-risk breast cancer family, here we show that SMYD3 phosphorylation by ATM enables the formation of a multiprotein complex including ATM, SMYD3, CHK2, and BRCA2, which is required for the final loading of RAD51 at DNA double-strand break sites and completion of homologous recombination (HR). Remarkably, SMYD3 pharmacological inhibition sensitizes HR-proficient cancer cells to PARP inhibitors, thereby extending the potential of the synthetic lethality approach in human tumors. SMYD3 phosphorylation by ATM favors the formation of HR complexes during DSB response SMYD3 mediates DSB repair by promoting RAD51 recruitment at DNA damage sites SMYD3 inhibition triggers a compensatory PARP-dependent DNA damage response Co-targeting SMYD3/PARP leads to synthetic lethality in HR-proficient cancer cells
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Affiliation(s)
- Paola Sanese
- Medical Genetics, National Institute of Gastroenterology "S. de Bellis" Research Hospital, Castellana Grotte, Bari 70013, Italy
| | - Candida Fasano
- Medical Genetics, National Institute of Gastroenterology "S. de Bellis" Research Hospital, Castellana Grotte, Bari 70013, Italy
| | - Giacomo Buscemi
- Institute of Molecular Genetics, IGM "Luigi Luca Cavalli-Sforza", National Research Council (CNR), Pavia 27100, Italy
| | - Cinzia Bottino
- Department of Biosciences, University of Milan, Milan 20133, Italy
| | - Silvia Corbetta
- Department of Biosciences, University of Milan, Milan 20133, Italy
| | - Edoardo Fabini
- Department of Pharmacy and Biotechnology, Alma Mater Studiorum University of Bologna, Bologna 40126, Italy.,BioChemoInformatics Unit, Institute of Organic Synthesis and Photoreactivity (ISOF), National Research Council (CNR), Bologna 40129, Italy
| | - Valentina Silvestri
- Department of Molecular Medicine, University of Roma "La Sapienza", Roma 00185, Italy
| | - Virginia Valentini
- Department of Molecular Medicine, University of Roma "La Sapienza", Roma 00185, Italy
| | - Vittoria Disciglio
- Medical Genetics, National Institute of Gastroenterology "S. de Bellis" Research Hospital, Castellana Grotte, Bari 70013, Italy
| | - Giovanna Forte
- Medical Genetics, National Institute of Gastroenterology "S. de Bellis" Research Hospital, Castellana Grotte, Bari 70013, Italy
| | - Martina Lepore Signorile
- Medical Genetics, National Institute of Gastroenterology "S. de Bellis" Research Hospital, Castellana Grotte, Bari 70013, Italy
| | - Katia De Marco
- Medical Genetics, National Institute of Gastroenterology "S. de Bellis" Research Hospital, Castellana Grotte, Bari 70013, Italy
| | - Stefania Bertora
- Medical Genetics, National Institute of Gastroenterology "S. de Bellis" Research Hospital, Castellana Grotte, Bari 70013, Italy
| | - Valentina Grossi
- Medical Genetics, National Institute of Gastroenterology "S. de Bellis" Research Hospital, Castellana Grotte, Bari 70013, Italy
| | - Ummu Guven
- Department of Biosciences, University of Milan, Milan 20133, Italy
| | - Natale Porta
- Department of Medical-Surgical Sciences and Biotechnology, Polo Pontino University of Roma "La Sapienza", Latina 04100, Italy
| | - Valeria Di Maio
- Department of Medical-Surgical Sciences and Biotechnology, Polo Pontino University of Roma "La Sapienza", Latina 04100, Italy
| | - Elisabetta Manoni
- BioChemoInformatics Unit, Institute of Organic Synthesis and Photoreactivity (ISOF), National Research Council (CNR), Bologna 40129, Italy
| | - Gianluigi Giannelli
- Medical Genetics, National Institute of Gastroenterology "S. de Bellis" Research Hospital, Castellana Grotte, Bari 70013, Italy
| | - Manuela Bartolini
- Department of Pharmacy and Biotechnology, Alma Mater Studiorum University of Bologna, Bologna 40126, Italy
| | - Alberto Del Rio
- BioChemoInformatics Unit, Institute of Organic Synthesis and Photoreactivity (ISOF), National Research Council (CNR), Bologna 40129, Italy.,Innovamol Consulting Srl, Modena 41123, Italy
| | | | - Laura Ottini
- Department of Molecular Medicine, University of Roma "La Sapienza", Roma 00185, Italy
| | - Cristiano Simone
- Medical Genetics, National Institute of Gastroenterology "S. de Bellis" Research Hospital, Castellana Grotte, Bari 70013, Italy.,Department of Biomedical Sciences and Human Oncology (DIMO), Medical Genetics; University of Bari Aldo Moro, Bari 70124, Italy
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4
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Casler JC, Papanikou E, Barrero JJ, Glick BS. Maturation-driven transport and AP-1-dependent recycling of a secretory cargo in the Golgi. J Cell Biol 2019; 218:1582-1601. [PMID: 30858194 PMCID: PMC6504904 DOI: 10.1083/jcb.201807195] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2018] [Revised: 12/20/2018] [Accepted: 01/29/2019] [Indexed: 12/21/2022] Open
Abstract
The Golgi cisternal maturation model predicts that secretory cargo proteins should be continuously present within the cisternae while resident Golgi proteins come and go. Casler et al. verify this prediction by tracking the passage of a fluorescent secretory cargo through the yeast Golgi. Golgi cisternal maturation has been visualized by fluorescence imaging of individual cisternae in the yeast Saccharomyces cerevisiae, but those experiments did not track passage of a secretory cargo. The expectation is that a secretory cargo will be continuously present within maturing cisternae as resident Golgi proteins arrive and depart. We tested this idea using a regulatable fluorescent secretory cargo that forms ER-localized aggregates, which dissociate into tetramers upon addition of a ligand. The solubilized tetramers rapidly exit the ER and then transit through early and late Golgi compartments before being secreted. Early Golgi cisternae form near the ER and become loaded with the secretory cargo. As predicted, cisternae contain the secretory cargo throughout the maturation process. An unexpected finding is that a burst of intra-Golgi recycling delivers additional secretory cargo molecules to cisternae during the early-to-late Golgi transition. This recycling requires the AP-1 adaptor, suggesting that AP-1 can recycle secretory cargo proteins as well as resident Golgi proteins.
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Affiliation(s)
- Jason C Casler
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL
| | - Effrosyni Papanikou
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL
| | - Juan J Barrero
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL
| | - Benjamin S Glick
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL
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5
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Yin Y, Garcia MR, Novak AJ, Saunders AM, Ank RS, Nam AS, Fisher LW. Surf4 (Erv29p) binds amino-terminal tripeptide motifs of soluble cargo proteins with different affinities, enabling prioritization of their exit from the endoplasmic reticulum. PLoS Biol 2018; 16:e2005140. [PMID: 30086131 PMCID: PMC6097701 DOI: 10.1371/journal.pbio.2005140] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Revised: 08/17/2018] [Accepted: 07/17/2018] [Indexed: 01/16/2023] Open
Abstract
Some secreted proteins that assemble into large complexes, such as extracellular matrices or hormones and enzymes in storage granules, must be kept at subaggregation concentrations during intracellular trafficking. We show surfeit locus protein 4 (Surf4) is the cargo receptor that establishes different steady-state concentrations for a variety of soluble cargo proteins within the endoplasmic reticulum (ER) through interaction with the amino-terminal tripeptides exposed after removal of leader sequences. We call this motif the ER-Exit by Soluble Cargo using Amino-terminal Peptide-Encoding motif (ER-ESCAPE motif). Proteins that most readily aggregate in the ER lumen (e.g., dentin sialophosphoprotein [DSPP] and amelogenin, X-linked [AMELX]) have strong ER-ESCAPE motifs to inhibit aggregate formation, while less susceptible cargo exhibits weaker motifs. Specific changes in a single amino acid of the tripeptide result in aggregate formation and failure to efficiently traffic cargo out of the ER. A logical subset of 8,000 possible tripeptides starting a model soluble cargo protein (growth hormone) established a continuum of steady-state ER concentrations ranging from low (i.e., high affinity for receptor) to the highest concentrations associated with bulk flow-limited trafficking observed for nonbinding motifs. Human cells lacking Surf4 no longer preferentially trafficked cargo expressing strong ER-ESCAPE motifs. Reexpression of Surf4 or expression of yeast's ortholog, ER-derived vesicles protein 29 (Erv29p), rescued enhanced ER trafficking in Surf4-null cells. Hence our work describes a new way of preferentially exporting soluble cargo out of the ER that maintains proteins below the concentrations at which they form damaging aggregates.
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Affiliation(s)
- Ying Yin
- Matrix Biochemistry Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Mekka R. Garcia
- Matrix Biochemistry Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Alexander J. Novak
- Matrix Biochemistry Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Allison M. Saunders
- Matrix Biochemistry Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Raira S. Ank
- Matrix Biochemistry Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Anna S. Nam
- Matrix Biochemistry Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Larry W. Fisher
- Matrix Biochemistry Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland, United States of America
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6
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Smith CEL, Murillo G, Brookes SJ, Poulter JA, Silva S, Kirkham J, Inglehearn CF, Mighell AJ. Deletion of amelotin exons 3-6 is associated with amelogenesis imperfecta. Hum Mol Genet 2016; 25:3578-3587. [PMID: 27412008 PMCID: PMC5179951 DOI: 10.1093/hmg/ddw203] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Revised: 06/17/2016] [Accepted: 06/21/2016] [Indexed: 11/15/2022] Open
Abstract
Amelogenesis imperfecta (AI) is a heterogeneous group of genetic conditions that result in defective dental enamel formation. Amelotin (AMTN) is a secreted protein thought to act as a promoter of matrix mineralization in the final stage of enamel development, and is strongly expressed, almost exclusively, in maturation stage ameloblasts. Amtn overexpression and Amtn knockout mouse models have defective enamel with no other associated phenotypes, highlighting AMTN as an excellent candidate gene for human AI. However, no AMTN mutations have yet been associated with human AI. Using whole exome sequencing, we identified an 8,678 bp heterozygous genomic deletion encompassing exons 3-6 of AMTN in a Costa Rican family segregating dominant hypomineralised AI. The deletion corresponds to an in-frame deletion of 92 amino acids, shortening the protein from 209 to 117 residues. Exfoliated primary teeth from an affected family member had enamel that was of a lower mineral density compared to control enamel and exhibited structural defects at least some of which appeared to be associated with organic material as evidenced using elemental analysis. This study demonstrates for the first time that AMTN mutations cause non-syndromic human AI and explores the human phenotype, comparing it with that of mice with disrupted Amtn function.
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Affiliation(s)
- Claire E L Smith
- Leeds Institute of Biomedical and Clinical Sciences, St James's University Hospital, University of Leeds, Leeds LS9 7TF, UK.,Department of Oral Biology, St James's University Hospital, University of Leeds, Leeds LS9 7TF, UK
| | - Gina Murillo
- University of Costa Rica, School of Dentistry, San Pedro, Costa Rica
| | - Steven J Brookes
- Department of Oral Biology, St James's University Hospital, University of Leeds, Leeds LS9 7TF, UK
| | - James A Poulter
- Leeds Institute of Biomedical and Clinical Sciences, St James's University Hospital, University of Leeds, Leeds LS9 7TF, UK
| | - Sandra Silva
- University of Costa Rica, Molecular Biology Cellular Centre (CBCM), San Pedro, Costa Rica and
| | - Jennifer Kirkham
- Department of Oral Biology, St James's University Hospital, University of Leeds, Leeds LS9 7TF, UK
| | - Chris F Inglehearn
- Leeds Institute of Biomedical and Clinical Sciences, St James's University Hospital, University of Leeds, Leeds LS9 7TF, UK
| | - Alan J Mighell
- Leeds Institute of Biomedical and Clinical Sciences, St James's University Hospital, University of Leeds, Leeds LS9 7TF, UK, .,School of Dentistry, University of Leeds, Leeds LS2 9LU, UK
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7
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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] [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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8
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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] [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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