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Vetriselvan Y, Manoharan A, Murugan M, Jayakumar S, Govindasamy C, Ravikumar S. In Silico Characterization of Pathogenic Homeodomain Missense Mutations in the PITX2 Gene. Biochem Genet 2024:10.1007/s10528-024-10836-z. [PMID: 38802693 DOI: 10.1007/s10528-024-10836-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2024] [Accepted: 05/09/2024] [Indexed: 05/29/2024]
Abstract
Paired homologous domain transcription factor 2 (PITX2) is critically involved in ocular and cardiac development. Mutations in PITX2 are consistently reported in association with Axenfeld-Rieger syndrome, an autosomal dominant genetic disorder and atrial fibrillation, a common cardiac arrhythmia. In this study, we have mined missense mutations in PITX2 gene from NCBI-dbSNP and Ensembl databases, evaluated the pathogenicity of the missense variants in the homeodomain and C-terminal region using five in silico prediction tools SIFT, PolyPhen2, GERP, Mutation Assessor and CADD. Fifteen homeodomain mutations G42V, G42R, R45W, S49Y, R53W, E53D, E55V, R62H, P65S, R69H, G75R, R84G, R86K, R87W, R91P were found to be highly pathogenic by both SIFT, PolyPhen2 were further functionally characterized using I-Mutant 2.0, Consurf, MutPred and Project Hope. The findings of the study can be used for prioritizing mutations in the context of genetic studies.
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Affiliation(s)
- Yogesh Vetriselvan
- Department of Medical Biotechnology, Aarupadai Veedu Medical College and Hospital, Vinayaka Mission's Research Foundation (DU), Kirumampakkam, Puducherry, 607403, India
| | - Aarthi Manoharan
- Department of Medical Biotechnology, Aarupadai Veedu Medical College and Hospital, Vinayaka Mission's Research Foundation (DU), Kirumampakkam, Puducherry, 607403, India
| | - Manoranjani Murugan
- Department of Medical Biotechnology, Aarupadai Veedu Medical College and Hospital, Vinayaka Mission's Research Foundation (DU), Kirumampakkam, Puducherry, 607403, India
| | - Swetha Jayakumar
- Department of Medical Biotechnology, Aarupadai Veedu Medical College and Hospital, Vinayaka Mission's Research Foundation (DU), Kirumampakkam, Puducherry, 607403, India
| | - Chandramohan Govindasamy
- Department of Community Health Sciences, College of Applied Medical Sciences, King Saud University, P.O. Box 10219, 11433, Riyadh, Saudi Arabia
| | - Sambandam Ravikumar
- Department of Medical Biotechnology, Aarupadai Veedu Medical College and Hospital, Vinayaka Mission's Research Foundation (DU), Kirumampakkam, Puducherry, 607403, India.
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Alkhammas AH, Al-Thuwaini TM, Al-Shuhaib MBS, Khazaal NM. Association of Novel C319T Variant of PITX2 Gene 3'UTR Region With Reproductive Performance in Awassi Sheep. Bioinform Biol Insights 2023; 17:11779322231179018. [PMID: 37313032 PMCID: PMC10259137 DOI: 10.1177/11779322231179018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2022] [Accepted: 05/13/2023] [Indexed: 06/15/2023] Open
Abstract
Several genes influence sheep's reproductive performance, among them the paired-like homeodomain transcription factor 2 (PITX2) gene. Thus, this study aimed to examine whether the variability within the PITX2 gene is associated with the reproductive performance of Awassi ewes. A total of 123 single-progeny ewes and 109 twin ewes were used to extract genomic DNA. An amplicon of 4 sequence fragments from exons 2, 4, 5 (upstream portion), and 5 (downstream portion) of the PITX2 gene was generated by polymerase chain reaction (PCR), 228, 304, 381, and 382 bp, respectively. Three genotypes of 382 bp amplicons were identified: CC, CT, and TT. Sequence analysis revealed a novel mutation in the CT genotype 319C > T. Statistical analysis revealed that single-nucleotide polymorphism (SNP) 319C > T was associated with reproductive performance. Single-nucleotide polymorphism 319C > T-carrying ewes had significantly (P ⩽ .01) lower litter sizes, twinning rates, lambing rates, and more days to lambing than those carrying CT and CC genotypes. Based on a logistic regression analysis, it was confirmed that the 319C > T SNP decreased litter size. Ewes with TT genotype produced fewer lambs than ewes with CT and CC genotypes. According to these results, the variant 319C> T SNP negatively affects the reproductive performance of Awassi sheep. Ewes carrying the 319C > T SNP have a lower litter size and are less prolific than those without the SNP.
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Affiliation(s)
- Ahmed H Alkhammas
- Department of Animal Production, College of Agriculture, Al-Qasim Green University, Al-Qasim, Iraq
| | - Tahreer M Al-Thuwaini
- Department of Animal Production, College of Agriculture, Al-Qasim Green University, Al-Qasim, Iraq
| | | | - Neam M Khazaal
- Department of Physiology, Biochemistry and Pharmacology, College of Veterinary Medicine, University of Baghdad, Baghdad, Iraq
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3
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Reis LM, Maheshwari M, Capasso J, Atilla H, Dudakova L, Thompson S, Zitano L, Lay-Son G, Lowry RB, Black J, Lee J, Shue A, Kremlikova Pourova R, Vaneckova M, Skalicka P, Jedlickova J, Trkova M, Williams B, Richard G, Bachman K, Seeley AH, Costakos D, Glaser TM, Levin AV, Liskova P, Murray JC, Semina EV. Axenfeld-Rieger syndrome: more than meets the eye. J Med Genet 2023; 60:368-379. [PMID: 35882526 PMCID: PMC9912354 DOI: 10.1136/jmg-2022-108646] [Citation(s) in RCA: 21] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Accepted: 07/15/2022] [Indexed: 12/11/2022]
Abstract
BACKGROUND Axenfeld-Rieger syndrome (ARS) is characterised by typical anterior segment anomalies, with or without systemic features. The discovery of causative genes identified ARS subtypes with distinct phenotypes, but our understanding is incomplete, complicated by the rarity of the condition. METHODS Genetic and phenotypic characterisation of the largest reported ARS cohort through comprehensive genetic and clinical data analyses. RESULTS 128 individuals with causative variants in PITX2 or FOXC1, including 81 new cases, were investigated. Ocular anomalies showed significant overlap but with broader variability and earlier onset of glaucoma for FOXC1-related ARS. Systemic anomalies were seen in all individuals with PITX2-related ARS and the majority of those with FOXC1-related ARS. PITX2-related ARS demonstrated typical umbilical anomalies and dental microdontia/hypodontia/oligodontia, along with a novel high rate of Meckel diverticulum. FOXC1-related ARS exhibited characteristic hearing loss and congenital heart defects as well as previously unrecognised phenotypes of dental enamel hypoplasia and/or crowding, a range of skeletal and joint anomalies, hypotonia/early delay and feeding disorders with structural oesophageal anomalies in some. Brain imaging revealed highly penetrant white matter hyperintensities, colpocephaly/ventriculomegaly and frequent arachnoid cysts. The expanded phenotype of FOXC1-related ARS identified here was found to fully overlap features of De Hauwere syndrome. The results were used to generate gene-specific management plans for the two types of ARS. CONCLUSION Since clinical features of ARS vary significantly based on the affected gene, it is critical that families are provided with a gene-specific diagnosis, PITX2-related ARS or FOXC1-related ARS. De Hauwere syndrome is proposed to be a FOXC1opathy.
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Affiliation(s)
- Linda M Reis
- Department of Pediatrics and Children's Research Institute, Medical College of Wisconsin and Children's Wisconsin, Milwaukee, Wisconsin, USA
| | - Mohit Maheshwari
- Department of Pediatric Radiology, Medical College of Wisconsin and Children's Wisconsin, Milwaukee, Wisconsin, USA
| | - Jenina Capasso
- Pediatric Ophthalmology and Ocular Genetics, Flaum Eye Institute, Golisano Children's Hospital and University of Rochester, Rochester, New York, USA
| | - Huban Atilla
- Department of Ophthalmology, School of Medicine, Ankara University, Ankara, Turkey
| | - Lubica Dudakova
- Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University and General University Hospital in Prague, Prague, Czech Republic
| | - Samuel Thompson
- Department of Pediatrics and Children's Research Institute, Medical College of Wisconsin and Children's Wisconsin, Milwaukee, Wisconsin, USA
| | - Lia Zitano
- Department of Medical Genetics, Spectrum Health, Grand Rapids, Michigan, USA
| | - Guillermo Lay-Son
- Unidad de Genética, División de Pediatría, Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - R Brian Lowry
- Department of Clinical Genetics, Alberta Children's Hospital, Calgary, Alberta, Canada
| | - Jennifer Black
- Center for Development, Behavior, and Genetics, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Joseph Lee
- Department of Family Medicine, McMaster University, Hamilton, Ontario, Canada
| | - Ann Shue
- Byers Eye Institute, Department of Ophthalmology, Stanford University and Stanford Children's Health, Stanford, California, USA
| | - Radka Kremlikova Pourova
- Department of Biology and Medical Genetics, Second Faculty of Medicine, Charles University and General University Hospital in Prague, Prague, Czech Republic
| | - Manuela Vaneckova
- Department of Radiology, First Faculty of Medicine, Charles University and General University Hospital in Prague, Prague, Czech Republic
| | - Pavlina Skalicka
- Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University and General University Hospital in Prague, Prague, Czech Republic
- Department of Ophthalmology, First Faculty of Medicine, Charles University and General University Hospital in Prague, Prague, Czech Republic
| | - Jana Jedlickova
- Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University and General University Hospital in Prague, Prague, Czech Republic
| | - Marie Trkova
- Gennet, Centre for Fetal Medicine and Reproductive Genetics, Prague, Czech Republic
| | | | | | - Kristine Bachman
- Department of Pediatrics, Geisinger Medical Center, Danville, Pennsylvania, USA
| | - Andrea H Seeley
- Department of Pediatrics, Geisinger Medical Center, Danville, Pennsylvania, USA
| | - Deborah Costakos
- Department of Ophthalmology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Thomas M Glaser
- Department of Cell Biology and Human Anatomy, UC-Davis School of Medicine, Davis, California, USA
| | - Alex V Levin
- Pediatric Ophthalmology and Ocular Genetics, Flaum Eye Institute, Golisano Children's Hospital and University of Rochester, Rochester, New York, USA
| | - Petra Liskova
- Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University and General University Hospital in Prague, Prague, Czech Republic
| | - Jeffrey C Murray
- Department of Pediatrics, University of Iowa, Iowa City, Iowa, USA
| | - Elena V Semina
- Department of Pediatrics and Children's Research Institute, Medical College of Wisconsin and Children's Wisconsin, Milwaukee, Wisconsin, USA
- Department of Ophthalmology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
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4
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Zhang Y, Chen X, Wang L, Sun X, Chen Y. Heterogeneity of Axenfeld-Rieger Syndrome: Molecular and Clinical Findings in Chinese Patients. Front Genet 2021; 12:732170. [PMID: 34745210 PMCID: PMC8564140 DOI: 10.3389/fgene.2021.732170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Accepted: 09/24/2021] [Indexed: 12/02/2022] Open
Abstract
Axenfeld–Rieger Syndrome (ARS) is a rare disease with a wide spectrum of ocular and systemic manifestations. The genetic spectrum of Chinese patients with ARS and genotype-phenotype correlations have yet to be described. To explore the molecular and clinical features in Chinese patients, fifty-five patients clinically diagnosed with ARS from independent families were recruited. Complete ophthalmic examinations and next generation sequencing of anterior segment dysgenesis associated genes were performed in all patients, and segregation in available relatives was verified using Sanger sequencing. 18 FOXC1 variants, 13 PITX2 variants, and two gross deletions spanning FOXC1 were detected in 35 out of 55 (63.6%) patients. 12 FOXC1 variants, 9 PITX2 variants, and two gross deletions were novel. There was a wide range of variability and severity in ocular and systemic manifestations displayed in our patients. Patients with FOXC1 variants were diagnosed at a younger age and had a lower prevalence of systemic manifestations than patients harboring PITX2 variants and those without variants. To our best knowledge, this is the largest study of Chinese patients with ARS to date. Our findings expand the genetic spectrum of ARS and reveal genotype-phenotype correlations in Chinese patients with ARS. Genetic and clinical heterogeneity were present in our patients. Awareness of the extensive characterization may aid in the clinical management and genetic counseling of patients with this rare disease.
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Affiliation(s)
- Youjia Zhang
- Department of Ophthalmology and Visual Science, Eye and ENT Hospital, Shanghai Medical College, Fudan University, Shanghai, China.,NHC Key Laboratory of Myopia, Chinese Academy of Medical Sciences, and Shanghai Key Laboratory of Visual Impairment and Restoration, Fudan University, Shanghai, China
| | - Xueli Chen
- Department of Ophthalmology and Visual Science, Eye and ENT Hospital, Shanghai Medical College, Fudan University, Shanghai, China
| | - Li Wang
- Department of Ophthalmology and Visual Science, Eye and ENT Hospital, Shanghai Medical College, Fudan University, Shanghai, China
| | - Xinghuai Sun
- Department of Ophthalmology and Visual Science, Eye and ENT Hospital, Shanghai Medical College, Fudan University, Shanghai, China.,NHC Key Laboratory of Myopia, Chinese Academy of Medical Sciences, and Shanghai Key Laboratory of Visual Impairment and Restoration, Fudan University, Shanghai, China.,State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, China
| | - Yuhong Chen
- Department of Ophthalmology and Visual Science, Eye and ENT Hospital, Shanghai Medical College, Fudan University, Shanghai, China.,NHC Key Laboratory of Myopia, Chinese Academy of Medical Sciences, and Shanghai Key Laboratory of Visual Impairment and Restoration, Fudan University, Shanghai, China
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5
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Yang Y, Li X, Wang J, Tan J, Fitzmaurice B, Nishina PM, Sun K, Tian W, Liu W, Liu X, Chang B, Zhu X. A missense mutation in Pitx2 leads to early-onset glaucoma via NRF2-YAP1 axis. Cell Death Dis 2021; 12:1017. [PMID: 34716303 PMCID: PMC8556256 DOI: 10.1038/s41419-021-04331-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 10/12/2021] [Accepted: 10/18/2021] [Indexed: 12/21/2022]
Abstract
Glaucoma is a leading cause of blindness, affecting 70 million people worldwide. Owing to the similarity in anatomy and physiology between human and mouse eyes and the ability to genetically manipulate mice, mouse models are an invaluable resource for studying mechanisms underlying disease phenotypes and for developing therapeutic strategies. Here, we report the discovery of a new mouse model of early-onset glaucoma that bears a transversion substitution c. G344T, which results in a missense mutation, p. R115L in PITX2. The mutation causes an elevation in intraocular pressure (IOP) and progressive death of retinal ganglion cells (RGC). These ocular phenotypes recapitulate features of pathologies observed in human glaucoma. Increased oxidative stress was evident in the inner retina. We demonstrate that the mutant PITX2 protein was not capable of binding to Nuclear factor-like 2 (NRF2), which regulates Pitx2 expression and nuclear localization, and to YAP1, which is necessary for co-initiation of transcription of downstream targets. PITX2-mediated transcription of several antioxidant genes were also impaired. Treatment with N-Acetyl-L-cysteine exerted a profound neuroprotective effect on glaucoma-associated neuropathies, presumably through inhibition of oxidative stress. Our study demonstrates that a disruption of PITX2 leads to glaucoma optic pathogenesis and provides a novel early-onset glaucoma model that will enable elucidation of mechanisms underlying the disease as well as to serve as a resource to test new therapeutic strategies.
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Affiliation(s)
- Yeming Yang
- Sichuan Provincial Key Laboratory for Human Disease Gene Study, Center for Medical Genetics, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, 610072, Chengdu, Sichuan, China
- Henan Eye Institute, Henan Eye Hospital, People's Hospital of Zhengzhou University, Henan Provincial People's Hospital, 450003, Zhengzhou, Henan, China
- Research Unit for Blindness Prevention of Chinese Academy of Medical Sciences (2019RU026), Sichuan Academy of Medical Sciences & Sichuan Provincial People's Hospital, 610072, Chengdu, Sichuan, China
| | - Xiao Li
- Sichuan Provincial Key Laboratory for Human Disease Gene Study, Center for Medical Genetics, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, 610072, Chengdu, Sichuan, China
| | - Jieping Wang
- The Jackson Laboratory, Bar Harbor, ME, 04609, USA
| | - Junkai Tan
- Xiamen Eye Center, Xiamen University, 361006, Xiamen, Fujian, China
| | | | | | - Kuanxiang Sun
- Sichuan Provincial Key Laboratory for Human Disease Gene Study, Center for Medical Genetics, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, 610072, Chengdu, Sichuan, China
| | - Wanli Tian
- Sichuan Provincial Key Laboratory for Human Disease Gene Study, Center for Medical Genetics, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, 610072, Chengdu, Sichuan, China
| | - Wenjing Liu
- Sichuan Provincial Key Laboratory for Human Disease Gene Study, Center for Medical Genetics, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, 610072, Chengdu, Sichuan, China
| | - Xuyang Liu
- Xiamen Eye Center, Xiamen University, 361006, Xiamen, Fujian, China.
- Department of Ophthalmology, Shenzhen People's Hospital, the 2nd Clinical Medical College, Jinan University, 518020, Shenzhen, China.
| | - Bo Chang
- The Jackson Laboratory, Bar Harbor, ME, 04609, USA.
| | - Xianjun Zhu
- Sichuan Provincial Key Laboratory for Human Disease Gene Study, Center for Medical Genetics, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, 610072, Chengdu, Sichuan, China.
- Henan Eye Institute, Henan Eye Hospital, People's Hospital of Zhengzhou University, Henan Provincial People's Hospital, 450003, Zhengzhou, Henan, China.
- Research Unit for Blindness Prevention of Chinese Academy of Medical Sciences (2019RU026), Sichuan Academy of Medical Sciences & Sichuan Provincial People's Hospital, 610072, Chengdu, Sichuan, China.
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Novel PITX2 Homeodomain-Contained Mutations from ATRIAL Fibrillation Patients Deteriorate Calcium Homeostasis. HEARTS 2021. [DOI: 10.3390/hearts2020020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Atrial fibrillation (AF) is the most common cardiac arrhythmia in the human population, with an estimated incidence of 1–2% in young adults but increasing to more than 10% in 80+ years patients. Pituitary Homeobox 2, Paired Like Homeodomain 2 (PITX2c) loss-of-function in mice revealed that this homeodomain (HD)-containing transcription factor plays a pivotal role in atrial electrophysiology and calcium homeostasis and point to PITX2 as a candidate gene for AF. To address this issue, we recruited 31 AF patients for genetic analyses of both the known risk alleles and PITX2c open reading frame (ORF) re-sequencing. We found two-point mutations in the homedomain of PITX2 and three other variants in the 5’untranslated region. A 65 years old male patient without 4q25 risk variants but with recurrent AF displayed two distinct HD-mutations, NM_000325.5:c.309G>C (Gln103His) and NM_000325.5:c.370G>A (Glu124Lys), which both resulted in a change within a highly conserved amino acid position. To address the functional impact of the PITX2 HD mutations, we generated plasmid constructs with mutated version of each nucleotide variant (MD4 and MD5, respectively) as well as a dominant negative control construct in which the PITX2 HD was lacking (DN). Functional analyses demonstrated PITX2c MD4 and PITX2c MD5 decreased Nppa-luciferase transactivation by 50% and 40%, respectively, similar to the PITX2c DN (50%), while Shox2 promoter repression was also impaired. Co-transactivation with other cardiac-enriched co-factors, such as Gata4 and Nkx2.5, was similarly impaired, further supporting the pivotal role of these mutations for correct PITX2c function. Furthermore, when expressed in HL1 cardiomyocyte cultures, the PITX2 mutants impaired endogenous expression of calcium regulatory proteins and induced alterations in sarcoplasmic reticulum (SR) calcium accumulation. This favored alternating and irregular calcium transient amplitudes, causing deterioration of the beat-to-beat stability upon elevation of the stimulation frequency. Overall this data demonstrate that these novel PITX2c HD-mutations might be causative of atrial fibrillation in the carrier.
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Williams AL, Bohnsack BL. The Ocular Neural Crest: Specification, Migration, and Then What? Front Cell Dev Biol 2021; 8:595896. [PMID: 33425902 PMCID: PMC7785809 DOI: 10.3389/fcell.2020.595896] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Accepted: 12/04/2020] [Indexed: 12/11/2022] Open
Abstract
During vertebrate embryonic development, a population of dorsal neural tube-derived stem cells, termed the neural crest (NC), undergo a series of morphogenetic changes and extensive migration to become a diverse array of cell types. Around the developing eye, this multipotent ocular NC cell population, called the periocular mesenchyme (POM), comprises migratory mesenchymal cells that eventually give rise to many of the elements in the anterior of the eye, such as the cornea, sclera, trabecular meshwork, and iris. Molecular cell biology and genetic analyses of congenital eye diseases have provided important information on the regulation of NC contributions to this area of the eye. Nevertheless, a complete understanding of the NC as a contributor to ocular development remains elusive. In addition, positional information during ocular NC migration and the molecular pathways that regulate end tissue differentiation have yet to be fully elucidated. Further, the clinical challenges of ocular diseases, such as Axenfeld-Rieger syndrome (ARS), Peters anomaly (PA) and primary congenital glaucoma (PCG), strongly suggest the need for better treatments. While several aspects of NC evolution have recently been reviewed, this discussion will consolidate the most recent current knowledge on the specification, migration, and contributions of the NC to ocular development, highlighting the anterior segment and the knowledge obtained from the clinical manifestations of its associated diseases. Ultimately, this knowledge can inform translational discoveries with potential for sorely needed regenerative therapies.
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Affiliation(s)
- Antionette L Williams
- Division of Ophthalmology, Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, IL, United States
| | - Brenda L Bohnsack
- Division of Ophthalmology, Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, IL, United States.,Department of Ophthalmology, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
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8
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Walter MA, Rezaie T, Hufnagel RB, Arno G. Ocular genetics in the genomics age. AMERICAN JOURNAL OF MEDICAL GENETICS PART C-SEMINARS IN MEDICAL GENETICS 2020; 184:860-868. [PMID: 32896097 DOI: 10.1002/ajmg.c.31844] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Revised: 08/14/2020] [Accepted: 08/17/2020] [Indexed: 12/29/2022]
Abstract
Current genetic screening methods for inherited eye diseases are concentrated on the coding exons of known disease genes (gene panels, clinical exome). These tests have a variable and often limited diagnostic rate depending on the clinical presentation, size of the gene panel and our understanding of the inheritance of the disorder (with examples described in this issue). There are numerous possible explanations for the missing heritability of these cases including undetected variants within the relevant gene (intronic, up/down-stream and structural variants), variants harbored in genes outside the targeted panel, intergenic variants, variants undetectable by the applied technology, complex/non-Mendelian inheritance, and nongenetic phenocopies. In this article we further explore and review methods to investigate these sources of missing heritability.
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Affiliation(s)
- Michael A Walter
- Department of Medical Genetics, University of Alberta, Edmonton, Alberta, Canada
| | - Tayebeh Rezaie
- National Center for Biotechnology Information, National Institutes of Health, Bethesda, Maryland, USA
| | - Robert B Hufnagel
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Gavin Arno
- University College London Institute of Ophthalmology, London, UK.,Moorfields Eye Hospital, London, UK
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9
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Lo Faro V, Siddiqui SN, Khan MI, Villanueva‐Mendoza C, Cortés‐González V, Jansonius N, Bergen AAB, Micheal S. Novel mutations in the PITX2 gene in Pakistani and Mexican families with Axenfeld-Rieger syndrome. Mol Genet Genomic Med 2020; 8:e1215. [PMID: 32400113 PMCID: PMC7336731 DOI: 10.1002/mgg3.1215] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Revised: 02/12/2020] [Accepted: 02/24/2020] [Indexed: 01/13/2023] Open
Abstract
PURPOSE Axenfeld-Rieger syndrome (ARS) is a rare autosomal dominant disorder that affects the anterior segment of the eye. The aim of this study was to examine the PITX2 gene to identify possible novel mutations in Pakistani and Mexican families affected by the ARS phenotype. METHODS Three unrelated probands with a diagnosis of ARS were recruited for this study. Genomic DNA was isolated from the peripheral blood of the probands and their family members. Polymerase chain reaction and Sanger sequencing were used for the analysis of coding exons and the flanking intronic regions of the PITX2 gene. Bioinformatics tools and database (VarSome, Provean, and MutationTaster, SIFT, PolyPhen-2, and HOPE) were evaluated to explore missense variants. RESULTS We identified novel heterozygous variations in the PITX2 gene that segregated with the ARS phenotype within the families. The variant NM_153426.2(PITX2):c.226G > T or p.(Ala76Ser) and the mutation NM_153426.2(PITX2):c.455G > A or p.(Cys152Tyr) were identified in two Pakistani pedigrees, and the mutation NM_153426.2(PITX2):c.242_265del or p.(Lys81_Gln88del), segregated in a Mexican family. CONCLUSION Our study extends the spectrum of PITX2 mutations in individuals with ARS, enabling an improved diagnosis of this rare but serious syndrome.
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Affiliation(s)
- Valeria Lo Faro
- Department of Clinical GeneticsUniversity Medical Center (UMC)University of Amsterdam (UvA)AmsterdamThe Netherlands
- Department of OphthalmologyUniversity Medical Center Groningen (UMCG)University of Groningen (RUG)GroningenThe Netherlands
| | - Sorath N. Siddiqui
- Department of Pediatric Ophthalmology and StrabismusAl‐Shifa Eye Trust HospitalRawalpindiPakistan
| | - Muhammad I. Khan
- Department of Human GeneticsDonders Institute for BrainCognition and BehaviourRadboud UMCNijmegenThe Netherlands
| | | | | | - Nomdo Jansonius
- Department of OphthalmologyUniversity Medical Center Groningen (UMCG)University of Groningen (RUG)GroningenThe Netherlands
| | - Arthur A. B. Bergen
- Department of Clinical GeneticsUniversity Medical Center (UMC)University of Amsterdam (UvA)AmsterdamThe Netherlands
- Department of OphthalmologyUniversitair Medische Centre (UMC)University of Amsterdam (UvA)AmsterdamThe Netherlands
- The Netherlands Institute for Neurosciences (NIN‐KNAW)AmsterdamThe Netherlands
| | - Shazia Micheal
- Department of Clinical GeneticsUniversity Medical Center (UMC)University of Amsterdam (UvA)AmsterdamThe Netherlands
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10
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Bai J, Lu Y, Lo A, Zhao J, Zhang H. PITX2 upregulation increases the risk of chronic atrial fibrillation in a dose-dependent manner by modulating IKs and ICaL -insights from human atrial modelling. ANNALS OF TRANSLATIONAL MEDICINE 2020; 8:191. [PMID: 32309338 PMCID: PMC7154416 DOI: 10.21037/atm.2020.01.90] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Background Functional analysis has shown that the paired-like homeodomain transcription factor 2 (PITX2) overexpression associated with atrial fibrillation (AF) leads to the slow delayed rectifier K+ current (IKs) increase and the L-type Ca2+ current (ICaL) reduction observed in isolated right atrial myocytes from chronic AF (CAF) patients. Through multiscale computational models, this study aimed to investigate the functional impact of the PITX2 overexpression on atrial electrical activity. Methods The well-known Courtemanche-Ramirez-Nattel (CRN) model of human atrial action potentials (APs) was updated to incorporate experimental data on alterations in IKs and ICaL due to the PITX2 overexpression. These cell models for sinus rhythm (SR) and CAF were then incorporated into homogeneous multicellular one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) tissue models. The proarrhythmic effects of the PITX2 overexpression were quantified with ion current profiles, AP morphology, AP duration (APD) restitution, conduction velocity restitution (CVR), wavelength (WL), vulnerable window (VW) for unidirectional conduction block, and minimal substrate size required to induce re-entry. Dynamic behaviors of spiral waves were characterized by measuring lifespan (LS), tip patterns and dominant frequencies. Results The IKs increase and the ICaL decrease arising from the PITX2 overexpression abbreviated APD and flattened APD restitution (APDR) curves in single cells. It reduced WL and increased CV at high excitation rates at the 1D tissue level. Although it had no effects on VW for initiating spiral waves, it decreased the minimal substrate size necessary to sustain re-entry. It also stabilized and accelerated spiral waves in 2D and 3D tissue models. Conclusions Electrical remodeling (IKs and ICaL) due to the PITX2 overexpression increases susceptibility to AF due to increased tissue vulnerability, abbreviated APD, shortened WL and altered CV, which, in combination, facilitate initiation and maintenance of spiral waves.
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Affiliation(s)
- Jieyun Bai
- Department of Electronic Engineering, College of Information Science and Technology, Jinan University, Guangzhou 510632, China
| | - Yaosheng Lu
- Department of Electronic Engineering, College of Information Science and Technology, Jinan University, Guangzhou 510632, China
| | - Andy Lo
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
| | - Jichao Zhao
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
| | - Henggui Zhang
- Biological Physics Group, School of Physics & Astronomy, University of Manchester, Manchester, UK
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11
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Nedelec B, Rozet JM, Fares Taie L. Genetic architecture of retinoic-acid signaling-associated ocular developmental defects. Hum Genet 2019; 138:937-955. [DOI: 10.1007/s00439-019-02052-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2019] [Accepted: 07/23/2019] [Indexed: 12/14/2022]
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12
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Novel PITX2 Mutations including a Mutation Causing an Unusual Ophthalmic Phenotype of Axenfeld-Rieger Syndrome. J Ophthalmol 2019; 2019:5642126. [PMID: 31341655 PMCID: PMC6636469 DOI: 10.1155/2019/5642126] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Revised: 02/23/2019] [Accepted: 03/06/2019] [Indexed: 12/22/2022] Open
Abstract
Purpose The aims of this study were to examine novel mutations in PITX2 and FOXC1 in Chinese patients with anterior segment dysgenesis (ASD) and to compare the clinical presentations of these mutations with previously reported associated phenotypes. Methods Twenty-six unrelated patients with different forms of ASD were enrolled from our paediatric and genetic eye clinic. The ocular manifestations of both eyes of each patient were recorded. Genomic DNA was prepared from venous leukocytes. All coding exons of PITX2 and FOXC1 were amplified by polymerase chain reaction (PCR) from genomic DNA and subjected to direct DNA sequencing. Analysis of mutations in control subjects was performed by heteroduplex single-strand conformation polymorphism (SSCP) analysis. Results Sequence analysis of the PITX2 gene revealed four mutations, including c.475_476delCT (P.L159VfsX39), c.64C > T (P.Q22X), c.296delG (P.R99PfsX56), and c.206G > A (P.R69H). The first three mutations were found to be novel. The c.475_476delCT (P.L159VfsX39) mutation, located at the 3' end of the PITX2-coding region, was identified in a Chinese Axenfeld-Rieger syndrome (ARS) patient who presented with an unusual severe phenotype of bilateral aniridia. The clinical characteristics, including the severity and manifestations of the patient's phenotype, were compared with reported PITX2-associated aniridia phenotypes of ARS in the literature. Conclusions These results expand the mutation spectrum of the PITX2 gene in patients with ARS. The PITX2 gene may be responsible for a significant portion of ARS with additional systemic defects in the Chinese population. This is the first reported case of a mutation at the 3' end of the PITX2-coding region extending the phenotypic consequences to bilateral aniridia. The traits of ARS could display tremendous variability in severity and manifestations due to the dominant-negative effect of PITX2. Our results further emphasize the importance of careful clinical and genetic analysis in determining mutation-disease associations and may lead to a better understanding of the role of PITX2 in ocular development.
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Mechakra A, Footz T, Walter M, Aránega A, Hernández-Torres F, Morel E, Millat G, Yang YQ, Chahine M, Chevalier P, Christé G. A Novel PITX2c Gain-of-Function Mutation, p.Met207Val, in Patients With Familial Atrial Fibrillation. Am J Cardiol 2019; 123:787-793. [PMID: 30558760 DOI: 10.1016/j.amjcard.2018.11.047] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2018] [Revised: 11/16/2018] [Accepted: 11/20/2018] [Indexed: 01/08/2023]
Abstract
Genome-wide studies have associated several genetic variants upstream of PITX2 on chromosome 4q25 with atrial fibrillation (AF), suggesting a potential role of PITX2 in AF. Our study aimed at identifying rare coding variants in PITX2 predisposing to AF. The Polymerase chain reaction sequencing of PITX2c was performed in 60 unrelated patients with idiopathic AF. The p.Met207Val variant was identified in 1 of 60 French patients with early onset AF and in none of 389 French referents. This variant, located in the inhibitory domain 1 distal to the homeodomain, was evaluated by the software MutationTaster as a disease-causing mutation with a probability of 0.999. Reporter gene assays demonstrated that p.Met207Val caused a 3.1-fold increase in transactivation activity of PITX2c in HeLa cells in comparison with its wild-type counterpart. When the variant was coexpressed with wild-type PITX2c in the HL-1 immortalized mouse atrial cell line, this gain-of-function caused an increase in the mRNA level of KCNH2 (2.6-fold), SCN1B (1.9-fold), GJA5 (3.1-fold), GJA1 (2.1-fold), and KCNQ1 in the homozygous form (1.8-fold). These genes encode for the IKr channel α subunit, the β-1 Na+ channel subunit, connexin 40, connexin 43 and the IKs channel α subunit, respectively. These conditions may contribute to the propensity to AF found in patients carrying the p.Met207Val variant. In conclusion, the present report is the first to associate a gain-of-function mutation of PITX2c with increased vulnerability to AF, therefore, restoration of normal PITX2c function may be a potential therapeutic target in AF patients.
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Affiliation(s)
- Asma Mechakra
- EA4612 Neurocardiologie, Université Lyon 1, Lyon, France
| | - Tim Footz
- Department of Medical Genetics, University of Alberta, Edmonton, Alberta, Canada
| | - Michael Walter
- Department of Medical Genetics, University of Alberta, Edmonton, Alberta, Canada
| | - Amelia Aránega
- Department of Experimental Biology, Faculty of Experimental Sciences, University of Jaén, Jaén, Spain
| | | | - Elodie Morel
- EA4612 Neurocardiologie, Université Lyon 1, Lyon, France
| | - Gilles Millat
- EA4612 Neurocardiologie, Université Lyon 1, Lyon, France
| | - Yi-Qing Yang
- Department of Cardiology, La-boratory of Cardiovascular Research and Central Laboratory, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai, China
| | - Mohamed Chahine
- Institut Universitaire en Santé Mentale, Québec City, Québec, Canada
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14
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Collins MM, Maischein HM, Dufourcq P, Charpentier M, Blader P, Stainier DY. Pitx2c orchestrates embryonic axis extension via mesendodermal cell migration. eLife 2018; 7:34880. [PMID: 29952749 PMCID: PMC6023614 DOI: 10.7554/elife.34880] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2018] [Accepted: 06/14/2018] [Indexed: 12/13/2022] Open
Abstract
Pitx2c, a homeodomain transcription factor, is classically known for its left-right patterning role. However, an early wave of pitx2 expression occurs at the onset of gastrulation in several species, indicating a possible earlier role that remains relatively unexplored. Here we show that in zebrafish, maternal-zygotic (MZ) pitx2c mutants exhibit a shortened body axis indicative of convergence and extension (CE) defects. Live imaging reveals that MZpitx2c mutants display less persistent mesendodermal migration during late stages of gastrulation. Transplant data indicate that Pitx2c functions cell non-autonomously to regulate this cell behavior by modulating cell shape and protrusive activity. Using transcriptomic analyses and candidate gene approaches, we identify transcriptional changes in components of the chemokine-ECM-integrin dependent mesendodermal migration network. Together, our results define pathways downstream of Pitx2c that are required during early embryogenesis and reveal novel functions for Pitx2c as a regulator of morphogenesis.
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Affiliation(s)
- Michelle M Collins
- Department of Developmental Genetics, Max Planck Institute for Heart and Lung Research, Bad Nauheim, Germany
| | - Hans-Martin Maischein
- Department of Developmental Genetics, Max Planck Institute for Heart and Lung Research, Bad Nauheim, Germany
| | - Pascale Dufourcq
- Centre de Biologie du Développement, Centre de Biologie Intégrative, Université Toulouse III - Paul Sabatier, CNRS, Toulouse, France
| | | | - Patrick Blader
- Centre de Biologie du Développement, Centre de Biologie Intégrative, Université Toulouse III - Paul Sabatier, CNRS, Toulouse, France
| | - Didier Yr Stainier
- Department of Developmental Genetics, Max Planck Institute for Heart and Lung Research, Bad Nauheim, Germany
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15
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Hendee KE, Sorokina EA, Muheisen SS, Reis LM, Tyler RC, Markovic V, Cuturilo G, Link BA, Semina EV. PITX2 deficiency and associated human disease: insights from the zebrafish model. Hum Mol Genet 2018; 27:1675-1695. [PMID: 29506241 PMCID: PMC5932568 DOI: 10.1093/hmg/ddy074] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Revised: 01/30/2018] [Accepted: 02/26/2018] [Indexed: 02/06/2023] Open
Abstract
The PITX2 (paired-like homeodomain 2) gene encodes a bicoid-like homeodomain transcription factor linked with several human disorders. The main associated congenital phenotype is Axenfeld-Rieger syndrome, type 1, an autosomal dominant condition characterized by variable defects in the anterior segment of the eye, an increased risk of glaucoma, craniofacial dysmorphism and dental and umbilical anomalies; in addition to this, one report implicated PITX2 in ring dermoid of the cornea and a few others described cardiac phenotypes. We report three novel PITX2 mutations-c.271C > T, p.(Arg91Trp); c.259T > C, p.(Phe87Leu); and c.356delA, p.(Gln119Argfs*36)-identified in independent families with typical Axenfeld-Rieger syndrome characteristics and some unusual features such as corneal guttata, Wolf-Parkinson-White syndrome, and hyperextensibility. To gain further insight into the diverse roles of PITX2/pitx2 in vertebrate development, we generated various genetic lesions in the pitx2 gene via TALEN-mediated genome editing. Affected homozygous zebrafish demonstrated congenital defects consistent with the range of PITX2-associated human phenotypes: abnormal development of the cornea, iris and iridocorneal angle; corneal dermoids; and craniofacial dysmorphism. In addition, via comparison of pitx2M64* and wild-type embryonic ocular transcriptomes we defined molecular changes associated with pitx2 deficiency, thereby implicating processes potentially underlying disease pathology. This analysis identified numerous affected factors including several members of the Wnt pathway and collagen types I and V gene families. These data further support the link between PITX2 and the WNT pathway and suggest a new role in regulation of collagen gene expression during development.
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Affiliation(s)
- Kathryn E Hendee
- Department of Pediatrics and Children’s Research Institute Medical College of Wisconsin and Children's Hospital of Wisconsin, Milwaukee, WI 53226, USA
- Department of Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Elena A Sorokina
- Department of Pediatrics and Children’s Research Institute Medical College of Wisconsin and Children's Hospital of Wisconsin, Milwaukee, WI 53226, USA
| | - Sanaa S Muheisen
- Department of Pediatrics and Children’s Research Institute Medical College of Wisconsin and Children's Hospital of Wisconsin, Milwaukee, WI 53226, USA
| | - Linda M Reis
- Department of Pediatrics and Children’s Research Institute Medical College of Wisconsin and Children's Hospital of Wisconsin, Milwaukee, WI 53226, USA
| | - Rebecca C Tyler
- Department of Pediatrics and Children’s Research Institute Medical College of Wisconsin and Children's Hospital of Wisconsin, Milwaukee, WI 53226, USA
| | - Vujica Markovic
- Faculty of Medicine, University of Belgrade, Serbia
- Clinical Centre of Serbia, University Eye Hospital, Belgrade, Serbia
| | - Goran Cuturilo
- Faculty of Medicine, University of Belgrade, Serbia
- Department of Medical Genetics, University Children’s Hospital, Belgrade, Serbia
| | - Brian A Link
- Department of Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, Milwaukee, WI 53226, USA
- Department of Ophthalmology, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Elena V Semina
- Department of Pediatrics and Children’s Research Institute Medical College of Wisconsin and Children's Hospital of Wisconsin, Milwaukee, WI 53226, USA
- Department of Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, Milwaukee, WI 53226, USA
- Department of Ophthalmology, Medical College of Wisconsin, Milwaukee, WI 53226, USA
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16
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Seifi M, Walter MA. Accurate prediction of functional, structural, and stability changes in PITX2 mutations using in silico bioinformatics algorithms. PLoS One 2018; 13:e0195971. [PMID: 29664915 PMCID: PMC5903617 DOI: 10.1371/journal.pone.0195971] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Accepted: 04/03/2018] [Indexed: 11/24/2022] Open
Abstract
Mutations in PITX2 have been implicated in several genetic disorders, particularly Axenfeld-Rieger syndrome. In order to determine the most reliable bioinformatics tools to assess the likely pathogenicity of PITX2 variants, the results of bioinformatics predictions were compared to the impact of variants on PITX2 structure and function. The MutPred, Provean, and PMUT bioinformatic tools were found to have the highest performance in predicting the pathogenicity effects of all 18 characterized missense variants in PITX2, all with sensitivity and specificity >93%. Applying these three programs to assess the likely pathogenicity of 13 previously uncharacterized PITX2 missense variants predicted 12/13 variants as deleterious, except A30V which was predicted as benign variant for all programs. Molecular modeling of the PITX2 homoedomain predicts that of the 31 known PITX2 variants, L54Q, F58L, V83F, V83L, W86C, W86S, and R91P alter PITX2's structure. In contrast, the remaining 24 variants are not predicted to change PITX2's structure. The results of molecular modeling, performed on all the PITX2 missense mutations located in the homeodomain, were compared with the findings of eight protein stability programs. CUPSAT was found to be the most reliable in predicting the effect of missense mutations on PITX2 stability. Our results showed that for PITX2, and likely other members of this homeodomain transcription factor family, MutPred, Provean, PMUT, molecular modeling, and CUPSAT can reliably be used to predict PITX2 missense variants pathogenicity.
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Affiliation(s)
- Morteza Seifi
- Department of Medical Genetics, Faculty of Medicine & Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Michael A. Walter
- Department of Medical Genetics, Faculty of Medicine & Dentistry, University of Alberta, Edmonton, Alberta, Canada
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17
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Seifi M, Walter MA. Axenfeld-Rieger syndrome. Clin Genet 2018; 93:1123-1130. [PMID: 28972279 DOI: 10.1111/cge.13148] [Citation(s) in RCA: 74] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2017] [Revised: 09/23/2017] [Accepted: 09/26/2017] [Indexed: 12/29/2022]
Abstract
Axenfeld-Rieger syndrome (ARS) is a clinically and genetically heterogeneous group of developmental disorders affecting primarily the anterior segment of the eye, often leading to secondary glaucoma. Patients with ARS may also present with systemic changes, including dental defects, mild craniofacial dysmorphism, and umbilical anomalies. ARS is inherited in an autosomal-dominant fashion; the underlying defect in 40% of patients is mutations in PITX2 or FOXC1. Here, an overview of the clinical spectrum of ARS is provided. As well, the known underlying genetic defects, clinical diagnostic possibilities, genetic counseling and treatments of ARS are discussed in detail.
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Affiliation(s)
- M Seifi
- Department of Medical Genetics, Faculty of Medicine and Dentistry, University of Alberta, Alberta, Edmonton, Canada
| | - M A Walter
- Department of Medical Genetics, Faculty of Medicine and Dentistry, University of Alberta, Alberta, Edmonton, Canada
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18
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Lewis CJ, Hedberg-Buenz A, DeLuca AP, Stone EM, Alward WL, Fingert JH. Primary congenital and developmental glaucomas. Hum Mol Genet 2017; 26:R28-R36. [PMID: 28549150 PMCID: PMC5886473 DOI: 10.1093/hmg/ddx205] [Citation(s) in RCA: 64] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Revised: 05/24/2017] [Accepted: 05/24/2017] [Indexed: 11/13/2022] Open
Abstract
Glaucoma is the leading cause of irreversible blindness worldwide. Although most glaucoma patients are elderly, congenital glaucoma and glaucomas of childhood are also important causes of visual disability. Primary congenital glaucoma (PCG) is isolated, non-syndromic glaucoma that occurs in the first three years of life and is a major cause of childhood blindness. Other early-onset glaucomas may arise secondary to developmental abnormalities, such as glaucomas that occur with aniridia or as part of Axenfeld-Rieger syndrome. Congenital and childhood glaucomas have strong genetic bases and disease-causing mutations have been discovered in several genes. Mutations in three genes (CYP1B1, LTBP2, TEK) have been reported in PCG patients. Axenfeld-Rieger syndrome is caused by mutations in PITX2 or FOXC1 and aniridia is caused by PAX6 mutations. This review discusses the roles of these genes in primary congenital glaucoma and glaucomas of childhood.
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Affiliation(s)
- Carly J. Lewis
- Department of Molecular Physiology and Biophysics, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
- Department of Ophthalmology and Visual Sciences, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
- Stephen A. Wynn Institute for Vision Research, 3111B Medical Education and Research Facility, University of Iowa, Iowa City, IA 52242, USA
| | - Adam Hedberg-Buenz
- Department of Molecular Physiology and Biophysics, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
- Department of Ophthalmology and Visual Sciences, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
- Stephen A. Wynn Institute for Vision Research, 3111B Medical Education and Research Facility, University of Iowa, Iowa City, IA 52242, USA
| | - Adam P. DeLuca
- Department of Ophthalmology and Visual Sciences, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
- Stephen A. Wynn Institute for Vision Research, 3111B Medical Education and Research Facility, University of Iowa, Iowa City, IA 52242, USA
| | - Edwin M. Stone
- Department of Ophthalmology and Visual Sciences, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
- Stephen A. Wynn Institute for Vision Research, 3111B Medical Education and Research Facility, University of Iowa, Iowa City, IA 52242, USA
| | - Wallace L.M. Alward
- Department of Ophthalmology and Visual Sciences, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
- Stephen A. Wynn Institute for Vision Research, 3111B Medical Education and Research Facility, University of Iowa, Iowa City, IA 52242, USA
| | - John H. Fingert
- Department of Ophthalmology and Visual Sciences, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
- Stephen A. Wynn Institute for Vision Research, 3111B Medical Education and Research Facility, University of Iowa, Iowa City, IA 52242, USA
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Moazzeni H, Akbari MT, Yazdani S, Elahi E. Expression of CXCL6 and BBS5 that may be glaucoma relevant genes is regulated by PITX2. Gene 2016; 593:76-83. [PMID: 27520585 DOI: 10.1016/j.gene.2016.08.019] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Revised: 07/31/2016] [Accepted: 08/08/2016] [Indexed: 12/26/2022]
Abstract
The transcription factor PITX2 is implicated in glaucoma pathology. In an earlier study we had used microarray analysis to identify genes in the trabecular meshwork (TM) that are affected by knock down of PITX2. Here, those studies were pursued to identify genes that are direct targets of PITX2 and that may be relevant to glaucoma. Initially, bioinformatics tools were used to select among the genes that had been affected by PITX2 knock down those that have PITX2 binding sites and that may be involved in glaucoma related functions. Subsequently, the effect of PITX2 was tested using the dual luciferase assay in four cell cultures including two primary TM cultures co-transfected with vectors containing promoter fragments of six candidate genes upstream of a luciferase gene and a vector that expressed PITX2. Finally, the effect of PITX2 on endogenous expression of two genes was assessed by over expression and knock down of PITX2 in TM cells. Thirty four genes were found to contain PITX2 binding sites in their putative promoter regions, and 16 were found to be associated with TM-specific and/or glaucoma associated functions. Results of dual luciferase assays confirmed that two of six genes tested were directly targeted by PITX2. The two genes were CXCL6 (chemokine (C-X-C motif) ligand 6) and BBS5 (Bardet-Biedl syndrome 5). Over expression and knock down of PITX2 showed that this transcription factor affects endogenous expression of these two genes in TM cells. CXCL6 encodes a pro-inflammatory cytokine, and many studies have suggested that cytokines and other immune system functions are involved in glaucoma pathogenesis. BBS5 is a member of the BBS family of genes that affect ciliary functions, and ciliary bodies in the anterior chamber of the eye produce the aqueous fluid that affects intraocular pressure. Immune related functions and intraocular pressure are both important components of glaucoma pathology. The role of PITX2 in glaucoma may be mediated partly by regulating the expression of CXCL6 and BBS5 and thus affecting immune functions and intraocular pressure.
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Affiliation(s)
- Hamidreza Moazzeni
- Department of Medical Genetics, Faculty of Medical Sciences, Tarbiat Modares University, P.O. Box. 14115-331, Tehran, Iran
| | - Mohammad Taghi Akbari
- Department of Medical Genetics, Faculty of Medical Sciences, Tarbiat Modares University, P.O. Box. 14115-331, Tehran, Iran.
| | - Shahin Yazdani
- Ophthalmic Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Elahe Elahi
- School of Biology, College of Science, University of Tehran, Tehran, Iran; Department of Biotechnology, College of Science, University of Tehran, Tehran, Iran.
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20
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Seifi M, Footz T, Taylor SAM, Elhady GM, Abdalla EM, Walter MA. Novel PITX2 gene mutations in patients with Axenfeld-Rieger syndrome. Acta Ophthalmol 2016; 94:e571-e579. [PMID: 27009473 DOI: 10.1111/aos.13030] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Accepted: 01/23/2016] [Indexed: 02/06/2023]
Abstract
PURPOSE Mutations in the bicoid-like transcription factor PITX2 gene often result in Axenfeld-Rieger syndrome (ARS), an autosomal-dominant inherited disorder. We report here the discovery and characterization of novel PITX2 deletions in a small kindred with ARS. METHODS Two familial patients (father and son) from a consanguineous family were examined in the present study. Patient DNA samples were screened for PITX2 mutations by DNA sequencing and for copy number variation by SYBR Green quantitative polymerase chain reaction (PCR) analysis. RESULTS We report a novel deletion involving the coding region of PITX2 in both patients. The minimum size of the deletion is 1 421 914 bp that spans one upstream regulatory element (CE4), PITX2 and a minimum of 13 neighbouring genes. The maximum size of the deletion is 3 789 983 bp. The proband (son) additionally possesses a novel 2-bp deletion in a non-coding exon of the remaining PITX2 allele predicted to alter correct splicing. CONCLUSION Our findings implicate a novel deletion of the PITX2 gene in the pathogenesis of ARS in the affected family. This ARS family presented with an atypical and extremely severe phenotype that resulted in four miscarriages and the death at 10 months of age of a sib of the proband. As the phenotypic manifestations in the proband are more severe than that of the father, we hypothesize that the deletion of the entire PITX2 allele plus a novel 2-bp deletion (observed in the proband) within the remaining PITX2 allele together contributed to the atypical ARS presentation in this family. This is the first study reporting on bi-allelic changes of PITX2 potentially contributing to a more severe ARS phenotype.
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Affiliation(s)
- Morteza Seifi
- Department of Medical Genetics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
| | - Tim Footz
- Department of Medical Genetics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
| | - Sherry A M Taylor
- Department of Medical Genetics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
| | - Ghada M Elhady
- Department of Human Genetics, Medical Research Institute, Alexandria University, Alexandria, Egypt
| | - Ebtesam M Abdalla
- Department of Human Genetics, Medical Research Institute, Alexandria University, Alexandria, Egypt
| | - Michael A Walter
- Department of Medical Genetics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada.
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Takeuchi K, Kitano M, Sakaida H, Masuda S. Novel syndrome with conductive hearing loss and congenital glaucoma in three generations. Auris Nasus Larynx 2016; 44:493-497. [PMID: 27552829 DOI: 10.1016/j.anl.2016.08.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Revised: 07/27/2016] [Accepted: 08/02/2016] [Indexed: 10/21/2022]
Abstract
The objective of this paper was to describe the clinical and otological findings in multiple members of a family with congenital glaucoma, cardiac anomaly, and conductive hearing loss due to ossicular chain anomalies. We performed a retrospective review of the medical charts and otological materials of multiple members of the same family. Congenital glaucoma and hearing loss were inherited by the proband and her daughter, son, and mother, suggesting autosomal dominant inheritance. The son and daughter also showed atrial septal defects. Exploratory tympanotomies revealed anomalies of the long process of the incus in the proband and her daughter, and tympanoplasty improved hearing loss in both patients. This represents the first description of coexisting congenital glaucoma and conductive hearing loss due to ossicular chain anomalies in multiple members of a single family.
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Affiliation(s)
- Kazuhiko Takeuchi
- Department of Otorhinolaryngology, Head & Neck Surgery, Mie University Graduate School of Medicine, Tsu, Japan.
| | - Masako Kitano
- Department of Otorhinolaryngology, Head & Neck Surgery, Mie University Graduate School of Medicine, Tsu, Japan
| | - Hiroshi Sakaida
- Department of Otorhinolaryngology, Head & Neck Surgery, Mie University Graduate School of Medicine, Tsu, Japan
| | - Sawako Masuda
- Department of Otorhinolaryngology, Mie National Hospital, Tsu, Japan
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22
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Browne JA, Yang R, Leir SH, Eggener SE, Harris A. Expression profiles of human epididymis epithelial cells reveal the functional diversity of caput, corpus and cauda regions. Mol Hum Reprod 2015; 22:69-82. [PMID: 26612782 DOI: 10.1093/molehr/gav066] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Accepted: 11/20/2015] [Indexed: 01/01/2023] Open
Abstract
STUDY HYPOTHESIS Region-specific transcriptional profiling of tissues and cultured epithelial cells from the human epididymis will predict functional specialization along the duct. STUDY FINDING We identified the molecular signature driving functions of the caput, corpus and cauda epithelium, and determined how these differ to establish the regional differentiation of the organ. WHAT IS KNOWN ALREADY The epithelium lining the human male genital ducts has a critical role in fertility. In particular, it controls the luminal environment in the epididymis, which is required for normal sperm maturation and reproductive competence. Studies in many animal species have largely informed our understanding of the molecular basis of epididymis function. However, there are substantial differences between species. STUDY DESIGN, SAMPLES/MATERIALS, METHODS Using RNA sequencing on biological replicates, we described gene expression profiles for tissue from each region of the epididymis and cultured epithelial cells derived from these regions. Bioinformatic tools were then utilized to identify differentially expressed genes (DEGs) between tissues and cells from the caput, corpus and cauda. MAIN RESULTS AND THE ROLE OF CHANCE The data showed that the caput is functionally divergent from the corpus and cauda, which have very similar transcriptomes. Interrogation of DEGs using gene ontology process enrichment analyses showed that processes of ion transport, response to hormone stimulus and urogenital tract development are more evident in the caput, while defense response processes are more important in the corpus/cauda. Consistent with these regional differences in epididymis function, we observed differential expression of transcription factors in the caput and corpus/cauda. LIMITATIONS, REASONS FOR CAUTION Cultured caput, corpus and cauda cells may not faithfully represent the same cells in the intact organ, due to loss of hormonal signals from the testis and communication from other cell types. WIDER IMPLICATIONS OF THE FINDINGS Our data provide a molecular characterization that will facilitate advances in understanding human epididymis epithelium biology in health and disease. They may also reveal the mechanisms coordinating epididymis luminal environment and sperm maturation. LARGE SCALE DATA Data deposited at http://www.ncbi.nlm.nih.gov/geo/GSE72986. STUDY FUNDING AND COMPETING INTERESTS This work was supported by the National Institutes of Health: R01HD068901 (PI: A.H.). The authors declare no conflict of interest.
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Affiliation(s)
- James A Browne
- Human Molecular Genetics Program, Lurie Children's Research Center, 2430 North Halsted Street, Box 211, Chicago, IL 60614, USA Department of Pediatrics, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Rui Yang
- Human Molecular Genetics Program, Lurie Children's Research Center, 2430 North Halsted Street, Box 211, Chicago, IL 60614, USA Department of Pediatrics, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Shih-Hsing Leir
- Human Molecular Genetics Program, Lurie Children's Research Center, 2430 North Halsted Street, Box 211, Chicago, IL 60614, USA Department of Pediatrics, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Scott E Eggener
- Section of Urology, University of Chicago Medical Center, Chicago, IL, USA
| | - Ann Harris
- Human Molecular Genetics Program, Lurie Children's Research Center, 2430 North Halsted Street, Box 211, Chicago, IL 60614, USA Department of Pediatrics, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
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23
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Yin HF, Fang XY, Jin CF, Yin JF, Li JY, Zhao SJ, Miao Q, Song FW. Identification of a novel frameshift mutation in PITX2 gene in a Chinese family with Axenfeld-Rieger syndrome. J Zhejiang Univ Sci B 2014; 15:43-50. [PMID: 24390743 PMCID: PMC3891117 DOI: 10.1631/jzus.b1300053] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2013] [Accepted: 07/01/2013] [Indexed: 11/11/2022]
Abstract
OBJECTIVE Axenfeld-Rieger syndrome (ARS) is phenotypically and genetically heterogeneous. In this study, we identified the underlying genetic defect in a Chinese family with ARS. METHODS A detailed family history and clinical data were recorded. The ocular phenotype was documented using slit-lamp photography and systemic anomalies were also documented where available. The genomic DNA was extracted from peripheral blood leukocytes. All coding exons and intron-exon junctions of paired-like homeodomain transcription factor 2 (PITX2) gene and the forkhead box C1 (FOXC1) gene were amplified by polymerase chain reaction (PCR) and screened for mutation by direct DNA sequencing. Variations detected in exon 5 of PITX2 were further evaluated with cloning sequencing. The exon 5 of PITX2 was also sequenced in 100 healthy controls, unrelated to the family, for comparison. Structural models of the wild type and mutant homeodomain of PITX2 were investigated by SWISS-MODEL. RESULTS Affected individuals exhibited variable ocular phenotypes, whereas the systemic anomalies were similar. After direct sequencing and cloning sequencing, a heterozygous deletion/insertion mutation c.198_201delinsTTTCT (p.M66Ifs*133) was revealed in exon 5 of PITX2. This mutation co-segregated with all affected individuals in the family and was not found either in unaffected family members or in 100 unrelated controls. CONCLUSIONS We detected a novel frameshift mutation p.M66Ifs*133 in PITX2 in a Chinese family with ARS. Although PITX2 mutations and polymorphisms have been reported from various ethnic groups, we report for the first time the identification of a novel deletion/insertion mutation that causes frameshift mutation in the homeodomain of PITX2 protein.
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Affiliation(s)
- Hou-fa Yin
- Eye Center, the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310009, China
- Zhejiang Provincial Key Lab of Ophthalmology, Hangzhou 310009, China
| | - Xiao-yun Fang
- Eye Center, the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310009, China
- Zhejiang Provincial Key Lab of Ophthalmology, Hangzhou 310009, China
| | - Chong-fei Jin
- Eye Center, the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310009, China
- Zhejiang Provincial Key Lab of Ophthalmology, Hangzhou 310009, China
| | - Jin-fu Yin
- Eye Center, the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310009, China
- Zhejiang Provincial Key Lab of Ophthalmology, Hangzhou 310009, China
| | - Jin-yu Li
- Eye Center, the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310009, China
- Zhejiang Provincial Key Lab of Ophthalmology, Hangzhou 310009, China
| | - Su-juan Zhao
- Eye Center, the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310009, China
- Zhejiang Provincial Key Lab of Ophthalmology, Hangzhou 310009, China
| | - Qi Miao
- Eye Center, the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310009, China
- Zhejiang Provincial Key Lab of Ophthalmology, Hangzhou 310009, China
| | - Feng-wei Song
- Eye Center, the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310009, China
- Zhejiang Provincial Key Lab of Ophthalmology, Hangzhou 310009, China
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24
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Yuan Y, Yeh LK, Liu H, Yamanaka O, Hardie WD, Kao WWY, Liu CY. Targeted overexpression of TGF-α in the corneal epithelium of adult transgenic mice induces changes in anterior segment morphology and activates noncanonical Wnt signaling. Invest Ophthalmol Vis Sci 2013; 54:1829-37. [PMID: 23412089 PMCID: PMC3626521 DOI: 10.1167/iovs.12-11477] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2012] [Accepted: 02/07/2013] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Transforming growth factor-alpha (TGF-α) transduces its signal through the epidermal growth factor receptor and is essential for corneal epithelial homeostasis. Previous studies have demonstrated that overexpression of TGF-α in the developing eye leads to anterior segment dysgenesis. However, the underlying mechanisms remain unclear. Here we examined the effects of TGF-α overexpression on adult ocular surface homeostasis. METHODS Binary Tet-On transgenic Krt12(rtTA)/tet-O-TGF-α mice were subjected to doxycycline (Dox) induction to overexpress TGF-α in the corneal epithelium. Intraocular pressure (IOP) was measured by noninvasive tonometry. The enucleated eyes of the experimental mice were subjected to histopathology, immunohistochemistry, and biochemistry examination. RESULTS Histologic and immunofluorescent examination showed that double-transgenic mice overexpressing TGF-α manifested peripheral anterior synechiae. Elevation of IOP, activation of glial cells, and loss of retinal ganglion cells were also observed. Quantitative real-time PCR revealed that the expressions of genes (RXRα, PITX2, and FOXC1) related to anterior segment dysgenesis were downregulated. Canonical Wnt signaling was suppressed, whereas noncanonical Wnt ligands (Wnt4 and Wnt5a) were upregulated. Increased myosin light chain phosphorylation suggested that noncanonical Wnt signaling is activated in affected eyes. CONCLUSIONS Overexpression of TGF-α in the corneal epithelium induces changes in anterior segment morphology. Corneal endothelial abnormalities are associated with the activation of the noncanonical Wnt and RhoA/ROCK signaling axis, indicating a potential application of RhoA/ROCK inhibitors as a therapeutic strategy for certain types of secondary angle-closure glaucoma.
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Affiliation(s)
- Yong Yuan
- From the
Crawley Vision Research Laboratory, Department of Ophthalmology, College of Medicine, University of Cincinnati, Cincinnati, Ohio; the
| | - Lung-Kun Yeh
- Department of Ophthalmology, Chang-Gung Memorial Hospital, Chang-Gung University College of Medicine, Linko, Taiwan; and
| | - Hongshan Liu
- From the
Crawley Vision Research Laboratory, Department of Ophthalmology, College of Medicine, University of Cincinnati, Cincinnati, Ohio; the
| | - Osamu Yamanaka
- From the
Crawley Vision Research Laboratory, Department of Ophthalmology, College of Medicine, University of Cincinnati, Cincinnati, Ohio; the
| | - William D. Hardie
- Divisions of Pulmonary Biology and Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Winston W.-Y. Kao
- From the
Crawley Vision Research Laboratory, Department of Ophthalmology, College of Medicine, University of Cincinnati, Cincinnati, Ohio; the
| | - Chia-Yang Liu
- From the
Crawley Vision Research Laboratory, Department of Ophthalmology, College of Medicine, University of Cincinnati, Cincinnati, Ohio; the
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25
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Reis LM, Tyler RC, Volkmann Kloss BA, Schilter KF, Levin AV, Lowry RB, Zwijnenburg PJG, Stroh E, Broeckel U, Murray JC, Semina EV. PITX2 and FOXC1 spectrum of mutations in ocular syndromes. Eur J Hum Genet 2012; 20:1224-33. [PMID: 22569110 PMCID: PMC3499749 DOI: 10.1038/ejhg.2012.80] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2011] [Revised: 02/22/2012] [Accepted: 02/29/2012] [Indexed: 02/01/2023] Open
Abstract
Anterior segment dysgenesis (ASD) encompasses a broad spectrum of developmental conditions affecting anterior ocular structures and associated with an increased risk for glaucoma. Various systemic anomalies are often observed in ASD conditions such as Axenfeld-Rieger syndrome (ARS) and De Hauwere syndrome. We report DNA sequencing and copy number analysis of PITX2 and FOXC1 in 76 patients with syndromic or isolated ASD and related conditions. PITX2 mutations and deletions were found in 24 patients with dental and/or umbilical anomalies seen in all. Seven PITX2-mutant alleles were novel including c.708_730del, the most C-terminal mutation reported to date. A second case of deletion of the distant upstream but not coding region of PITX2 was identified, highlighting the importance of this recently discovered mechanism for ARS. FOXC1 deletions were observed in four cases, three of which demonstrated hearing and/or heart defects, including a patient with De Hauwere syndrome; no nucleotide mutations in FOXC1 were identified. Review of the literature identified several other patients with 6p25 deletions and features of De Hauwere syndrome. The 1.3-Mb deletion of 6p25 presented here defines the critical region for this phenotype and includes the FOXC1, FOXF2, and FOXQ1 genes. In summary, PITX2 or FOXC1 disruptions explained 63% of ARS and 6% of other ASD in our cohort; all affected patients demonstrated additional systemic defects with PITX2 mutations showing a strong association with dental and/or umbilical anomalies and FOXC1 with heart and hearing defects. FOXC1 deletion was also found to be associated with De Hauwere syndrome.
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Affiliation(s)
- Linda M Reis
- Department of Pediatrics and Children's Research Institute, Milwaukee, WI, USA
| | - Rebecca C Tyler
- Department of Pediatrics and Children's Research Institute, Milwaukee, WI, USA
| | - Bethany A Volkmann Kloss
- Department of Pediatrics and Children's Research Institute, Milwaukee, WI, USA
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Kala F Schilter
- Department of Pediatrics and Children's Research Institute, Milwaukee, WI, USA
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Alex V Levin
- Pediatric Ophthalmology and Ocular Genetics, Wills Eye Institute, Thomas Jefferson University, Philadelphia, PA, USA
| | - R Brian Lowry
- Department of Medical Genetics, Alberta Children's Hospital and University of Calgary, Calgary, AB, Canada
| | - Petra J G Zwijnenburg
- Department of Clinical Genetics, VU University Medical Centre, Amsterdam, HV, The Netherlands
| | - Eliza Stroh
- Pediatric Ophthalmology and Ocular Genetics, Wills Eye Institute, Thomas Jefferson University, Philadelphia, PA, USA
| | - Ulrich Broeckel
- Department of Pediatrics and Children's Research Institute, Milwaukee, WI, USA
| | - Jeffrey C Murray
- Department of Pediatrics, The University of Iowa, Iowa City, IA, USA
| | - Elena V Semina
- Department of Pediatrics and Children's Research Institute, Milwaukee, WI, USA
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI, USA
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26
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Doerdelmann T, Kojetin DJ, Baird-Titus JM, Solt LA, Burris TP, Rance M. Structural and biophysical insights into the ligand-free Pitx2 homeodomain and a ring dermoid of the cornea inducing homeodomain mutant. Biochemistry 2012; 51:665-76. [PMID: 22224469 PMCID: PMC3264736 DOI: 10.1021/bi201639x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The homeodomain-containing transcription factor Pitx2 (pituitary homeobox protein 2) is present in many developing embryonic tissues, including the heart. Its homeodomain is responsible for the recognition and binding to target DNA sequences and thus constitutes a major functional unit in the Pitx2 protein. Nuclear magnetic resonance techniques were employed to determine the solution structure of the native Pitx2 homeodomain and a R24H mutant that causes autosomal dominantly inherited ring dermoid of the cornea syndrome. The structures reveal that both isoforms possess the canonical homeodomain fold. However, the R24H mutation results in a 2-fold increase in DNA binding affinity and a 5 °C decrease in thermal stability, while changing the dynamic environment of the homeodomain only locally. When introduced into full-length Pitx2c, the mutation results in an only 25% loss of transactivation activity. Our data correlate well with clinical observations suggesting a milder deficiency for the R24H mutation compared to those of other Pitx2 homeodomain mutations.
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Affiliation(s)
- Thomas Doerdelmann
- University of Cincinnati, Department of Molecular Genetics, Biochemistry and Microbiology, 231 Albert Sabin Way, Cincinnati, OH 45267, USA
| | - Douglas J. Kojetin
- University of Cincinnati, Department of Molecular Genetics, Biochemistry and Microbiology, 231 Albert Sabin Way, Cincinnati, OH 45267, USA
- The Scripps Research Institute, Scripps Florida, Department of Molecular Therapeutics, 130 Scripps Way, Jupiter, FL 33458, USA
| | - Jamie M. Baird-Titus
- College of Mount St. Joseph, Department of Chemistry, 5701 Delhi Road, Cincinnati, OH 45233, USA
| | - Laura A. Solt
- The Scripps Research Institute, Scripps Florida, Department of Molecular Therapeutics, 130 Scripps Way, Jupiter, FL 33458, USA
| | - Thomas P. Burris
- The Scripps Research Institute, Scripps Florida, Department of Molecular Therapeutics, 130 Scripps Way, Jupiter, FL 33458, USA
| | - Mark Rance
- University of Cincinnati, Department of Molecular Genetics, Biochemistry and Microbiology, 231 Albert Sabin Way, Cincinnati, OH 45267, USA
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27
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Bohnsack BL, Kasprick DS, Kish PE, Goldman D, Kahana A. A zebrafish model of axenfeld-rieger syndrome reveals that pitx2 regulation by retinoic acid is essential for ocular and craniofacial development. Invest Ophthalmol Vis Sci 2012; 53:7-22. [PMID: 22125274 PMCID: PMC3292384 DOI: 10.1167/iovs.11-8494] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2011] [Revised: 10/09/2011] [Accepted: 11/10/2011] [Indexed: 11/24/2022] Open
Abstract
PURPOSE The homeobox transcription factor PITX2 is a known regulator of mammalian ocular development, and human PITX2 mutations are associated with Axenfeld-Rieger syndrome (ARS). However, the treatment of patients with ARS remains mostly supportive and palliative. METHODS The authors used molecular genetic, pharmacologic, and embryologic techniques to study the biology of ARS in a zebrafish model that uses transgenes to mark neural crest and muscle cells in the head. RESULTS The authors demonstrated in vivo that pitx2 is a key downstream target of retinoic acid (RA) in craniofacial development, and this pathway is required for coordinating neural crest, mesoderm, and ocular development. pitx2a knockdown using morpholino oligonucleotides disrupts jaw and pharyngeal arch formation and recapitulates ocular characteristics of ARS, including corneal and iris stroma maldevelopment. These phenotypes could be rescued with human PITX2A mRNA, demonstrating the specificity of the knockdown and evolutionary conservation of pitx2a function. Expression of the ARS dominant negative human PITX2A K50E allele also caused ARS-like phenotypes. Similarly, inhibition of RA synthesis in the developing eye (genetic or pharmacologic) disrupted craniofacial and ocular development, and human PITX2A mRNA partially rescued these defects. CONCLUSIONS RA regulation of pitx2 is essential for coordinating interactions among neural crest, mesoderm, and developing eye. The marked evolutionary conservation of Pitx2 function in eye and craniofacial development makes zebrafish a potentially powerful model of ARS, amenable to in vivo experimentation and development of potential therapies.
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Affiliation(s)
- Brenda L Bohnsack
- Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, Michigan, USA
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28
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Tonoki H, Harada N, Shimokawa O, Yosozumi A, Monzaki K, Satoh K, Kosaki R, Sato A, Matsumoto N, Iizuka S. Axenfeld-Rieger anomaly and Axenfeld-Rieger syndrome: clinical, molecular-cytogenetic, and DNA array analyses of three patients with chromosomal defects at 6p25. Am J Med Genet A 2011; 155A:2925-32. [PMID: 22009788 DOI: 10.1002/ajmg.a.33858] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2010] [Accepted: 11/29/2010] [Indexed: 12/26/2022]
Abstract
Clinical phenotypes of and genetic aberrations in three unrelated Japanese patients with Axenfeld-Rieger anomalies and various accompanying malformations of systemic organs are described. GTG-banded chromosome analysis showed terminal deletions of the short arm of chromosome 6 in two patients and an inversion, inv(6)(p25q14), in the other. FISH and DNA array analyses revealed that the two patients with deletions had 5.0-5.7 Mb and 6.6 Mb 6p terminal deletions, respectively, and FOXC1 was apparently deleted in both patients. In the other patient, the inversion breakpoint at 6p25 was estimated to be in or very close to the FOXC1 locus, but DNA array analysis did not reveal a deletion around the breakpoint. Common extraocular findings in these patients included broad forehead, brachycephaly, hypertelorism, downslanting palpebral fissures, small anteverted nose, and cardiac defects. Two patients also exhibited autistic characteristics. The two patients with deletions exhibited poor muscle tone and developmental delays. Most of these extraocular findings were similar to those found in previous patients with FOXC1 mutations and distinct from those found in patients with PITX2 mutations, who frequently develop umbilical and dental anomalies. We suggest that the psychomotor retardation is a clinical manifestation associated with a deletion of multiple contiguous genes in the 6p terminus and that this phenomenon is similar to the 6p25 deletion syndrome. Understanding the relationship between genetic lesions and the spectrum of extraocular findings in patients with Axenfeld-Rieger anomalies may lead to better clinical management.
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Affiliation(s)
- Hidefumi Tonoki
- Section of Clinical Genetics, Department of Pediatrics, Tenshi Hospital, Sapporo, Japan.
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29
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Strungaru MH, Footz T, Liu Y, Berry FB, Belleau P, Semina EV, Raymond V, Walter MA. PITX2 is involved in stress response in cultured human trabecular meshwork cells through regulation of SLC13A3. Invest Ophthalmol Vis Sci 2011; 52:7625-33. [PMID: 21873665 PMCID: PMC3183983 DOI: 10.1167/iovs.10-6967] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2010] [Revised: 05/17/2011] [Accepted: 06/04/2011] [Indexed: 10/17/2022] Open
Abstract
PURPOSE Mutations of the PITX2 gene cause Axenfeld-Rieger syndrome (ARS) and glaucoma. In this study, the authors investigated genes directly regulated by the PITX2 transcription factor to gain insight into the mechanisms underlying these disorders. METHODS RNA from nonpigmented ciliary epithelium cells transfected with hormone-inducible PITX2 and activated by mifepristone was subjected to microarray analyses. Data were analyzed using dCHIP algorithms to detect significant differences in expression. Genes with significantly altered expression in multiple microarray experiments in the presence of activated PITX2 were subjected to in silico and biochemical analyses to validate them as direct regulatory targets. One target gene was further characterized by studying the effect of its knockdown in a cell model of oxidative stress, and its expression in zebrafish embryos was analyzed by in situ hybridization. RESULTS Solute carrier family 13 sodium-dependent dicarboxylate transporter member 3 (SLC13A3) was identified as 1 of 47 potential PITX2 target genes in ocular cells. PITX2 directly regulates SLC13A3 expression, as demonstrated by luciferase reporter and chromatin immunoprecipitation assays. Reduction of PITX2 or SLC13A3 levels by small interfering RNA (siRNA)-mediated knockdown augmented the death of transformed human trabecular meshwork cells exposed to hydrogen peroxide. Zebrafish slc13a3 is expressed in anterior ocular regions in a pattern similar to that of pitx2. CONCLUSIONS The results indicate that SLC13A3 is a direct downstream target of PITX2 transcriptional regulation and that levels of PITX2 and SLC13A3 modulate responses to oxidative stress in ocular cells.
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Affiliation(s)
| | - Tim Footz
- From the Departments of Medical Genetics and
| | - Yi Liu
- Department of Pediatrics and Children's Research Institute, Medical College of Wisconsin and Children's Hospital of Wisconsin, Milwaukee, Wisconsin
| | - Fred B. Berry
- From the Departments of Medical Genetics and
- Surgery, University of Alberta, Edmonton, Alberta, Canada
| | - Pascal Belleau
- Department of Molecular Medicine, Université Laval, Québec City, Quebec, Canada; and
| | - Elena V. Semina
- Department of Pediatrics and Children's Research Institute, Medical College of Wisconsin and Children's Hospital of Wisconsin, Milwaukee, Wisconsin
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Vincent Raymond
- Department of Molecular Medicine, Université Laval, Québec City, Quebec, Canada; and
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30
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Yang SY, Yang XL, Yao LF, Wang HB, Sun CK. Effect of CpG methylation on DNA binding protein: molecular dynamics simulations of the homeodomain PITX2 bound to the methylated DNA. J Mol Graph Model 2011; 29:920-7. [PMID: 21498098 DOI: 10.1016/j.jmgm.2011.03.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2010] [Revised: 03/02/2011] [Accepted: 03/03/2011] [Indexed: 10/18/2022]
Abstract
A large number of studies have argued that aberrant CpG methylation is associated with some human cancers. One possible mechanism of the cancer caused by CpG methylation is the gene repression, which is a binding-inhibition of the sequence-specific transcription factors bound to specific DNA-binding sites. Exploring the effects of CpG methylation on the structure and the thermodynamic property of DNA-binding transcription factors will help to gain an insight into how CpG methylation affects the repression of gene transcription in cancer. We have performed molecular dynamics (MD) simulations and free energy calculations of the protein bound to the native or the methylated DNA, in which the solution structure of the K50-class homeodomain PITX2 bound to DNA was used as a template. The simulation results indicate that the methylated CpG located at the DNA major groove can enhance the protein-DNA interactions, and the residue side-chains near the methylated CpG pair appear to have an unusually high affinity with DNA. The structural analysis and calculated energy values demonstrate that the binding-induced structural changes were further encouraged as the CpG methylation upon the complexation. Moreover, the CpG methylation may reduce the unfavorable effect of the conformational entropy and increase the electrostatic contribution to the binding free energy of DNA-PITX2. The changes in specific binding sites and the excessive affinity between DNA and protein caused by the CpG methylation could affect the gene transcriptional activity.
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Affiliation(s)
- Si-Ya Yang
- School of Chemistry and Chemical Engineering, Qujing Normal University, Sanjiang Road, Qinig District, Qujing City 655011, Yunnan Province, PR China.
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31
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Zacharias AL, Gage PJ. Canonical Wnt/β-catenin signaling is required for maintenance but not activation of Pitx2 expression in neural crest during eye development. Dev Dyn 2010; 239:3215-25. [PMID: 20960542 PMCID: PMC3073314 DOI: 10.1002/dvdy.22459] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/16/2010] [Indexed: 12/28/2022] Open
Abstract
Pitx2 is a paired-like homeodomain gene that acts as a key regulator of eye development. Despite its significance, upstream regulation of Pitx2 expression during eye development remains incompletely understood. We use neural crest-specific ablation of Ctnnb1 to demonstrate that canonical Wnt signaling is not required for initial activation of Pitx2 in neural crest. However, canonical Wnt signaling is subsequently required to maintain Pitx2 expression in the neural crest. Eye development in Ctnnb1-null mice appears grossly normal early but significant phenotypes emerge following loss of Pitx2 expression. LEF-1 and β-catenin bind Pitx2 promoter sequences in ocular neural crest, indicating a likely direct effect of canonical Wnt signaling on Pitx2 expression. Combining our data with previous reports, we propose a model wherein a sequential code of retinoic acid followed by canonical Wnt signaling are required for activation and maintenance of Pitx2 expression, respectively. Other key transcription factors in the neural crest, including Foxc1, do not require intact canonical Wnt signaling.
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Affiliation(s)
- Amanda L. Zacharias
- Departments of Ophthalmology & Visual Sciences, and Cell & Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48105
| | - Philip J. Gage
- Departments of Ophthalmology & Visual Sciences, and Cell & Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48105
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32
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Avdonin PP, Grigoryan EN, Markitantova YV. Transcriptional factor Pitx2: Localization during triton retina regeneration. BIOL BULL+ 2010. [DOI: 10.1134/s1062359010030039] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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33
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Tümer Z, Bach-Holm D. Axenfeld-Rieger syndrome and spectrum of PITX2 and FOXC1 mutations. Eur J Hum Genet 2009; 17:1527-39. [PMID: 19513095 PMCID: PMC2987033 DOI: 10.1038/ejhg.2009.93] [Citation(s) in RCA: 172] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2008] [Revised: 01/23/2009] [Accepted: 03/17/2009] [Indexed: 01/09/2023] Open
Abstract
Axenfeld-Rieger syndrome (ARS) is a rare autosomal dominant disorder, which encompasses a range of congential malformations affecting the anterior segment of the eye. ARS shows genetic heterogeneity and mutations of the two genes, PITX2 and FOXC1, are known to be associated with the pathogenesis. There are several excellent reviews dealing with the complexity of the phenotype and genotype of ARS. In this study, we will attempt to give a brief review of the clinical features and the relevant diagnostic approaches, together with a detailed review of published PITX2 and FOXC1 mutations.
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Affiliation(s)
- Zeynep Tümer
- The Kennedy Center, Medical Genetics Laboratory, Glostrup, Denmark.
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Gage PJ, Qian M, Wu D, Rosenberg KI. The canonical Wnt signaling antagonist DKK2 is an essential effector of PITX2 function during normal eye development. Dev Biol 2008; 317:310-24. [PMID: 18367164 PMCID: PMC2387126 DOI: 10.1016/j.ydbio.2008.02.030] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2007] [Revised: 02/12/2008] [Accepted: 02/14/2008] [Indexed: 10/22/2022]
Abstract
Local control of cell signaling activity and integration of inputs from multiple signaling pathways are central for normal development but the underlying mechanisms remain poorly understood. Here we show that Dkk2, encoding an antagonist of canonical Wnt signaling, is an essential downstream target of the PITX2 homeodomain transcription factor in neural crest during eye development. Canonical Wnt signaling is ectopically activated in central ocular surface ectoderm and underlying mesenchyme in Pitx2- and Dkk2-deficient mice. General ocular surface ectoderm identity is maintained during development in Dkk2-deficient mice but peripheral fates, including conjunctival goblet cells and eyelash follicles, are ectopically permitted within more central structures and eyelids are hypomorphic. Loss of DKK2 results in ectopic blood vessels within the periocular mesenchyme and PITX2 expression remains persistently high, providing evidence for a negative feedback loop. Collectively, these data suggest that activation of Dkk2 by PITX2 provides a mechanism to locally suppress canonical Wnt signaling activity during eye development, a paradigm that may be a model for achieving local or transient inhibition of pathway activity elsewhere during embryogenesis. We further propose a model placing PITX2 as an essential integration node between retinoic acid and canonical Wnt signaling during eye development.
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Affiliation(s)
- Philip J Gage
- Department of Ophthalmology and Visual Sciences, University of Michigan Medical School, Ann Arbor, MI 48105, USA.
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Cianfarani S. Neuroendocrine complications of central nervous system malformations. HANDBOOK OF CLINICAL NEUROLOGY 2008; 87:433-50. [PMID: 18809037 DOI: 10.1016/s0072-9752(07)87023-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2023]
Affiliation(s)
- Stefano Cianfarani
- Rina Balducci Center of Pediatric Endocrinology, Department of Public Health and Cell Biology, Tor Vergata University of Rome, Via Montpellier I, Rome, Italy.
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Abstract
Anterior segment dysgenesis (ASD) is a failure of the normal development of the tissues of the anterior segment of the eye. It leads to anomalies in the structure of the mature anterior segment, associated with an increased risk of glaucoma and corneal opacity. Several different gene mutations have been identified underlying these anomalies with the majority of ASD genes encoding transcriptional regulators. In this review, the role of the ASD genes, PITX2 and FOXC1, is considered in relation to the embryology of the anterior segment, the biochemical function of these proteins, and their role in development and disease aetiology. The emerging view is that these genes act in concert to specify a population of mesenchymal progenitor cells, mainly of neural crest origin, as they migrate anteriorly around the embryonic optic cup. These same genes then regulate mesenchymal cell differentiation to give rise to distinct anterior segment tissues. Development appears critically sensitive to gene dosage, and variation in the normal level of transcription factor activity causes a range of anterior segment anomalies. Interplay between PITX2 and FOXC1 in the development of different anterior segment tissues may partly explain the phenotypic variability and the genetic heterogeneity characteristic of ASD.
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Affiliation(s)
- J C Sowden
- Developmental Biology Unit, University College London Institute of Child Health and Great Ormond Street Hospital for Children NHS Trust, London, UK.
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Sakazume S, Sorokina E, Iwamoto Y, Semina EV. Functional analysis of human mutations in homeodomain transcription factor PITX3. BMC Mol Biol 2007; 8:84. [PMID: 17888164 PMCID: PMC2093940 DOI: 10.1186/1471-2199-8-84] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2007] [Accepted: 09/21/2007] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The homeodomain-containing transcription factor PITX3 was shown to be essential for normal eye development in vertebrates. Human patients with point mutations in PITX3 demonstrate congenital cataracts along with anterior segment defects in some cases when one allele is affected and microphthalmia with brain malformations when both copies are mutated. The functional consequences of these human mutations remain unknown. RESULTS We studied the PITX3 mutant proteins S13N and G219fs to determine the type and severity of functional defects. Our results demonstrate alterations in DNA-binding profiles and/or transactivation activities and suggest a partial loss-of-function in both mutants with the G219fs form being more severely affected. No anomalies in cellular distribution and no dominant-negative effects were discovered for these mutants. Interestingly, the impairment of the G219fs activity varied between different ocular cell lines. CONCLUSION The G219fs mutation was found in multiple families affected with congenital cataracts along with anterior segment malformations in many members. Our data suggest that the presence/severity of anterior segment defects in families affected with G219fs may be determined by secondary factors that are expressed in the developing anterior segment structures and may modify the effect(s) of this mutation. The S13N mutant showed only minor alteration of transactivation ability and DNA binding pattern and may represent a rare polymorphism in the PITX3 gene. A possible contribution of this mutation to human disease needs to be further investigated.
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Affiliation(s)
- Satoru Sakazume
- Department of Pediatrics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
- Human and Molecular Genetics Center, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
- Division of Clinical Genetics, Gunma Children's Medical Center, Shibukawa, Gunma, Japan
| | - Elena Sorokina
- Department of Pediatrics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
- Human and Molecular Genetics Center, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
- Children's Research Institute, Children's Hospital of Wisconsin and Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
| | - Yoshiki Iwamoto
- Human and Molecular Genetics Center, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
- Department of Urology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
- Department of Surgical Research, Beckman Research Institute of the City of Hope, Duarte, CA 91010-3000, USA
| | - Elena V Semina
- Department of Pediatrics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
- Human and Molecular Genetics Center, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
- Children's Research Institute, Children's Hospital of Wisconsin and Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
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Kniestedt C, Taralczak M, Thiel MA, Stuermer J, Baumer A, Gloor BP. A novel PITX2 mutation and a polymorphism in a 5-generation family with Axenfeld-Rieger anomaly and coexisting Fuchs' endothelial dystrophy. Ophthalmology 2006; 113:1791.e1-8. [PMID: 16876867 DOI: 10.1016/j.ophtha.2006.05.017] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2005] [Revised: 05/15/2006] [Accepted: 05/15/2006] [Indexed: 11/26/2022] Open
Abstract
PURPOSE To investigate the clinical and genetic appearance of Axenfeld-Rieger anomaly or syndrome (ARAS) and Fuchs' endothelial dystrophy (FED) in a 5-generation pedigree coexpressing both pathologic features in a large number of family members. DESIGN Observational case-control and DNA linkage and screening study. PARTICIPANTS Of 114 family members, 50 underwent clinical investigation and DNA analysis between July 2001 and March 2004. METHODS Linkage at the PITX2 locus was demonstrated using a number of microsatellites mapping to the critical region 4q25 to 4q26. The PITX2 gene was subsequently screened for mutations in all investigated family members. MAIN OUTCOME MEASURE Linkage of the ARAS and FED phenotype and mutation detection in the PITX2 gene. RESULTS Twenty-seven patients were identified as being affected by ARAS. Fuchs' endothelial dystrophy was found in 19 patients. Fifteen patients presented both kinds of anomaly. Deoxyribonucleic acid sequencing revealed 2 heteroallelic DNA variants that segregated together (on the same allele) and were present in all severely affected ARAS individuals. The first variant, g.20913G>T, assumed to be the causative mutation for ARAS, causes amino acid substitution at codon 137 (G137V). A statistically significant 2-point logarithm of the odds score of 4.06 was obtained with marker D4S406. The second variant is likely a polymorphism in the intron between exons 2 and 3 (IVS2+8delCinsGTT) and was detected in heterozygous form in 20% of control individuals. CONCLUSION This gene analysis revealed a novel PITX2 mutation and a polymorphism in a family with ARAS. Whether FED, also manifested in the severely affected individuals, is due to a different but cosegregating gene is to be determined.
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Affiliation(s)
- Christoph Kniestedt
- Department of Ophthalmology, Cantonal Hospital Winterthur, Winterthur, Switzerland.
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Quentien MH, Barlier A, Franc JL, Pellegrini I, Brue T, Enjalbert A. Pituitary transcription factors: from congenital deficiencies to gene therapy. J Neuroendocrinol 2006; 18:633-42. [PMID: 16879162 DOI: 10.1111/j.1365-2826.2006.01461.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Despite the existence of interspecies phenotypic variability, animal models have yielded valuable insights into human pituitary diseases. Studies on Snell and Jackson mice known to have growth hormone, prolactin and thyroid-stimulating hormone deficiencies involving the hypoplastic pituitary gland have led to identifying alterations of the pituitary specific POU homeodomain Pit-1 transcription factor gene. The human phenotype associated with rare mutations in this gene was found to be similar to that of these mice mutants. Terminal differentiation of lactotroph cells and direct regulation of the prolactin gene both require interactions between Pit-1 and cell type specific partners, including panpituitary transcriptional regulators such as Pitx1 and Pitx2. Synergistic activation of the prolactin promoter by Pitx factors and Pit-1 is involved not only in basal condition, but also in responsiveness to forskolin, thyrotrophin-releasing-hormone and epidermal growth factor. In corticotroph cells, Pitx1 interacts with Tpit. Tpit mutations have turned out to be the main molecular cause of neonatal isolated adrenocorticotrophin deficiency. This finding supports the idea that Tpit plays an essential role in the differentiation of the pro-opiomelanocortin pituitary lineage. The effects of Pit-1 are not restricted to hormone gene regulation because this factor also contributes to cell division and protects the cell from programmed cell death. Lentiviral vectors expressing a Pit-1 dominant negative mutant induced time- and dose-dependent cell death in somatotroph and lactotroph adenomas in vitro. Gene transfer by lentiviral vectors should provide a promising step towards developing an efficient specific therapeutic approach by which a gene therapy programme for treating human pituitary adenomas could be based.
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Affiliation(s)
- M H Quentien
- ICNE-UMR6544-CNRS-Université de la Méditerranée, Institut Jean Roche, Marseille, France.
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Maciolek NL, Alward WLM, Murray JC, Semina EV, McNally MT. Analysis of RNA splicing defects in PITX2 mutants supports a gene dosage model of Axenfeld-Rieger syndrome. BMC MEDICAL GENETICS 2006; 7:59. [PMID: 16834779 PMCID: PMC1553432 DOI: 10.1186/1471-2350-7-59] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/03/2006] [Accepted: 07/11/2006] [Indexed: 12/02/2022]
Abstract
BACKGROUND Axenfeld-Rieger syndrome (ARS) is associated with mutations in the PITX2 gene that encodes a homeobox transcription factor. Several intronic PITX2 mutations have been reported in Axenfeld-Rieger patients but their effects on gene expression have not been tested. METHODS We present two new families with recurrent PITX2 intronic mutations and use PITX2c minigenes and transfected cells to address the hypothesis that intronic mutations effect RNA splicing. Three PITX2 mutations have been analyzed: a G>T mutation within the AG 3' splice site (ss) junction associated with exon 4 (IVS4-1G>T), a G>C mutation at position +5 of the 5' (ss) of exon 4 (IVS4+5G>C), and a previously reported A>G substitution at position -11 of 3'ss of exon 5 (IVS5-11A>G). RESULTS Mutation IVS4+5G>C showed 71% retention of the intron between exons 4 and 5, and poorly expressed protein. Wild-type protein levels were proportionally expressed from correctly spliced mRNA. The G>T mutation within the exon 4 AG 3'ss junction shifted splicing exclusively to a new AG and resulted in a severely truncated, poorly expressed protein. Finally, the A>G substitution at position -11 of the 3'ss of exon 5 shifted splicing exclusively to a newly created upstream AG and resulted in generation of a protein with a truncated homeodomain. CONCLUSION This is the first direct evidence to support aberrant RNA splicing as the mechanism underlying the disorder in some patients and suggests that the magnitude of the splicing defect may contribute to the variability of ARS phenotypes, in support of a gene dosage model of Axenfeld-Rieger syndrome.
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Affiliation(s)
- Nicole L Maciolek
- Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
| | - Wallace LM Alward
- Department of Ophthalmology, University of Iowa, Iowa City, IA 52242, USA
| | - Jeffrey C Murray
- Department of Pediatrics, University of Iowa, Iowa City, IA 52242, USA
| | - Elena V Semina
- Department of Pediatrics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
| | - Mark T McNally
- Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
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Abstract
The anterior segment dysgeneses are an ill-defined group of ocular developmental abnormalities that share some common features and have a high prevalence of glaucoma. Current classification of what are and what are not anterior segment dysgeneses seems to vary and our knowledge of them is incomplete. As the limits of classical clinical medicine based on evaluation of signs and symptoms are reached, further advancements increasingly will come from molecular medicine and genetics. In this article we review the normal and abnormal development of the anterior segment (concentrating primarily upon neural crest derived dysgeneses), describe the various clinical entities produced and their diagnosis, and discuss the current knowledge of the genetics of these disorders. We also suggest a new approach to the classification of anterior segment dysgeneses, based upon the embryological contribution to the formation of the anterior segment of the eye.
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Affiliation(s)
- Faisal Idrees
- Institute of Child Health, University College London, UK
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Berry FB, Lines MA, Oas JM, Footz T, Underhill DA, Gage PJ, Walter MA. Functional interactions between FOXC1 and PITX2 underlie the sensitivity to FOXC1 gene dose in Axenfeld-Rieger syndrome and anterior segment dysgenesis. Hum Mol Genet 2006; 15:905-19. [PMID: 16449236 DOI: 10.1093/hmg/ddl008] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Axenfeld-Rieger ocular dysgenesis is associated with mutations of the human PITX2 and FOXC1 genes, which encode transcription factors of the homeodomain and forkhead types, respectively. We have identified a functional link between FOXC1 and PITX2 which we propose underpins the similar Axenfeld-Rieger phenotype caused by mutations of these genes. FOXC1 and PITX2A physically interact, and this interaction requires crucial functional domains on both proteins: the C-terminal activation domain of FOXC1 and the homeodomain of PITX2. Immunofluorescence further shows PITX2A and FOXC1 to be colocalized within a common nuclear subcompartment. Furthermore, PITX2A can function as a negative regulator of FOXC1 transactivity. This work ties both proteins into a common pathway and offers an explanation of why increased FOXC1 gene dosage produces a phenotype resembling that of PITX2 deletions and mutations. Ocular phenotypes arise despite the deregulated expression of FOXC1-target genes through mutations in FOXC1 or PITX2. Ultimately, PITX2 loss of function mutations have a compound effect: the reduced expression of PITX2-target genes coupled with the extensive activation of FOXC1-regulated targets. Our findings indicate that the functional interaction between FOXC1 and PITX2A underlies the sensitivity to FOXC1 gene dosage in Axenfeld-Rieger syndrome and related anterior segment dysgeneses.
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Affiliation(s)
- Fred B Berry
- Department of Ophthalmology, University of Alberta, Edmonton, Alberta, Canada, T6G 2H7.
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Saadi I, Toro R, Kuburas A, Semina E, Murray JC, Russo AF. An unusual class of PITX2 mutations in Axenfeld-Rieger syndrome. BIRTH DEFECTS RESEARCH. PART A, CLINICAL AND MOLECULAR TERATOLOGY 2006; 76:175-81. [PMID: 16498627 PMCID: PMC4023635 DOI: 10.1002/bdra.20226] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND Mutations in the PITX2 homeobox gene are known to contribute to Axenfeld-Rieger syndrome (ARS), an autosomal-dominant developmental disorder. Although most mutations are in the homeodomain and result in a loss of function, there is a growing subset in the C-terminal domain that has not yet been characterized. These mutations are of particular interest because the C-terminus has both inhibitory and stimulatory activities. METHODS In this study we used a combination of in vitro DNA binding and transfection reporter assays to investigate the fundamental issue of whether C-terminal mutations result in gain or loss of function at a cellular level. RESULTS We report a new frameshift mutation in the PITX2 allele that predicts a truncated protein lacking most of the C-terminal domain (D122FS). This newly reported mutant and another ARS C-terminal mutant (W133Stop) both have greater binding than wild-type to the bicoid element. Of interest, the mutants yielded approximately 5-fold greater activation of the prolactin promoter in CHO cells, even though the truncated proteins were expressed at lower levels than the wild-type protein. The truncated proteins also had greater than wild-type activity in 2 other cell lines, including the LS8 oral epithelial line that expresses the endogenous Pitx2 gene. CONCLUSIONS The results indicate that the PITX2 C-terminal domain has inhibitory activity and support the notion that ARS may also be caused by gain-of-function mutations.
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Affiliation(s)
- Irfan Saadi
- Genetics Program, University of Iowa, Iowa City, Iowa
| | - Rafael Toro
- Genetics Program, University of Iowa, Iowa City, Iowa
| | - Adisa Kuburas
- Department of Physiology and Biophysics, University of Iowa, Iowa City, Iowa
| | - Elena Semina
- Department of Pediatrics, University of Iowa, Iowa City, Iowa
| | - Jeffrey C. Murray
- Genetics Program, University of Iowa, Iowa City, Iowa
- Department of Pediatrics, University of Iowa, Iowa City, Iowa
| | - Andrew F. Russo
- Genetics Program, University of Iowa, Iowa City, Iowa
- Department of Physiology and Biophysics, University of Iowa, Iowa City, Iowa
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Functional analysis of three genetic disorder related PITX2 mutants. CHINESE SCIENCE BULLETIN-CHINESE 2006. [DOI: 10.1007/s11434-005-1374-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Evans AL, Gage PJ. Expression of the homeobox gene Pitx2 in neural crest is required for optic stalk and ocular anterior segment development. Hum Mol Genet 2005; 14:3347-59. [PMID: 16203745 DOI: 10.1093/hmg/ddi365] [Citation(s) in RCA: 133] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Heterozygous mutations in the homeobox gene, PITX2, result in ocular anterior segment defects and a high incidence of early-onset glaucoma. Pitx2 is expressed in both the neural crest and the mesoderm-derived precursors of the periocular mesenchyme. Complete loss of function in mice results in agenesis or severe disruption of periocular mesenchyme structures and extrinsic defects in early optic nerve development. However, the specific requirements for Pitx2 in neural crest versus mesoderm could not be determined using these mice, and only roles in the initial stages of eye development could be assessed due to early embryonic lethality. To determine the specific roles of Pitx2 in the neural crest precursor pool, we generated neural crest-specific Pitx2 knockout mice (Pitx2-ncko). Because Pitx2-nkco mice are viable, we also analyzed gene function in later eye development. Pitx2 is intrinsically required in neural crest for specification of corneal endothelium, corneal stroma and the sclera. Pitx2 function in neural crest is also required for normal development of ocular blood vessels. Pitx2-ncko mice exhibit a unique optic nerve phenotype in which the eyes are progressively displaced towards the midline until they are directly attached to the ventral hypothalamus. As Pitx2 is not expressed in the optic stalk, an essential function of PITX2 protein in neural crest is to regulate an extrinsic factor(s) required for development of the optic nerve. We propose a revised model of optic nerve development and new mechanisms that may underlie the etiology of glaucoma in Axenfeld-Rieger patients.
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Affiliation(s)
- Amanda L Evans
- Department of Ophthalmology and Visual Sciences, University of Michigan Medical School, Ann Arbor, 48109, USA
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Abstract
The authors describe the case of a 10-year-old girl presenting with Axenfeld-Rieger syndrome (ARS), a rare autosomal dominant condition. The patient showed severe hypodontia, microdontia and short roots. Early diagnosis of the syndrome from its dento-facial and systemic features is important so that subsequent ocular complications may be prevented.
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Affiliation(s)
- E M O'Dwyer
- Department of Oral and Maxillofacial Surgery, Arrowe Park Hospital, Upton, UK
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Charles MA, Suh H, Hjalt TA, Drouin J, Camper SA, Gage PJ. PITX genes are required for cell survival and Lhx3 activation. Mol Endocrinol 2005; 19:1893-903. [PMID: 15761027 DOI: 10.1210/me.2005-0052] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The PITX family of transcription factors regulate the development of many organs. Pitx1 mutants have a mild pituitary phenotype, but Pitx2 is necessary for the development of Rathke's pouch, expression of essential transcription factors in gonadotropes, and expansion of the Pit1 lineage. We report that lack of Pitx2 causes the pouch to undergo excessive cell death, resulting in severe pituitary hypoplasia. Transgenic overexpression of PITX2 in the pituitary can increase the gonadotrope population, suggesting that the absolute concentration of PITX2 is important for normal pituitary cell lineage expansion. We show that PITX1 and PITX2 proteins are present in similar expression patterns throughout pituitary development and in the mature pituitary. Both transcription factors are preferentially expressed in adult gonadotropes and thyrotropes, suggesting the possibility of overlap in maintenance of adult pituitary functions within these cell types. Double knockouts of Pitx1 and Pitx2 exhibit severe pituitary hypoplasia and fail to express the transcription factor LHX3. This indicates that these PITX genes are upstream of Lhx3 and have compensatory roles during development. Thus, the combined dosage of these PITX family members is vital for pituitary development, and their persistent coexpression in the adult pituitary suggests a continued role in maintenance of pituitary function.
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Affiliation(s)
- Michael A Charles
- 4301 MSRB III, 1500 West Medical Center Drive, University of Michigan Medical School, Ann Arbor, MI 48109-0638, USA
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Zhu X, Lin CR, Prefontaine GG, Tollkuhn J, Rosenfeld MG. Genetic control of pituitary development and hypopituitarism. Curr Opin Genet Dev 2005; 15:332-40. [PMID: 15917210 DOI: 10.1016/j.gde.2005.04.011] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2005] [Accepted: 04/12/2005] [Indexed: 10/25/2022]
Abstract
The pituitary gland functions as a relay between the hypothalamus and peripheral target organs that regulate basic physiological functions, including growth, the stress response, reproduction, metabolism and lactation. The development of the pituitary gland has been studied extensively in mice, and has begun to be explored in zebrafish, an animal model system amenable to forward genetics. Multiple signaling molecules and transcription factors, expressed in overlapping but distinct spatial and temporal patterns, are required at various stages of pituitary development. Defects in this precisely regulated genetic program lead to diverse pituitary dysfunction. The animal models have greatly enhanced our understanding of molecular mechanisms underlying pituitary development in addition to congenital pituitary disorders in humans.
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Affiliation(s)
- Xiaoyan Zhu
- Howard Hughes Medical Institute, Department and School of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
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Holmberg J, Liu CY, Hjalt TA. PITX2 gain-of-function in Rieger syndrome eye model. THE AMERICAN JOURNAL OF PATHOLOGY 2004; 165:1633-41. [PMID: 15509533 PMCID: PMC1618668 DOI: 10.1016/s0002-9440(10)63420-7] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 07/15/2004] [Indexed: 01/15/2023]
Abstract
The human autosomal-dominant disorder Axenfeld-Rieger syndrome presents with defects in development of the eyes, teeth, and umbilicus. The eye manifests with iris ruptures, irido-corneal adhesions, cloudy corneas, and glaucoma. Transcription factors such as PITX2 and FOXC1 have been found to carry point mutations, causing the disorder. However, for approximately 40% of the cases, the pathogenesis is unknown. It has been reported that some mutations in PITX2 increase transactivation, whereas most mutations cause defects in DNA binding or transactivation. It is not known whether up-regulation of PITX2 activity can cause the disorder as well. Here we test this hypothesis directly by overexpressing PITX2A as a transgene in mouse corneal mesenchyme and iris, using keratocan-flanking sequences. The mice presented with corneal opacification, corneal hypertrophy, irido-corneal adhesions, and severely degenerated retina, resembling glaucoma. The corneal hypertrophy also resembles the corneal hypertrophy of Pitx2-/- mice. Control transgenic mice carrying point mutations T68P or K88E in PITX2A were normal. These findings indicate a novel pathogenetic mechanism in which excess corneal and iridal PITX2A cause glaucoma and anterior defects that closely resemble Axenfeld-Rieger syndrome.
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Affiliation(s)
- Johan Holmberg
- Lund University, Department of Cell and Molecular Biology, Section for Cell and Developmental Biology, BMC B12, Tornavägen 10, SE-22184 Lund, Sweden
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