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A novel PITX2 mutation in a Chinese family with Axenfeld-Rieger syndrome.

ABSTRACT: PURPOSE: Axenfeld-Rieger syndrome (ARS) is an autosomal dominant disorder characterized by extraocular anomalies and developmental defects of the anterior segment. PITX2 (paired-like homeodomain transcription factor 2) is considered the major causative gene. In this study, we characterized the molecular defect in PITX2 in a Chinese family with ARS. METHODS: Two generations of the family with ARS were enrolled in the present study. In addition to ophthalmologic examinations, polymerase chain reaction (PCR) amplification and nucleotide sequencing of all coding exons of PITX2 were performed. Exon 5 (region 1) was also sequenced in 100 healthy controls unrelated to the family for comparison. RESULTS: A novel PITX2 mutation, c.840G>T, was identified in all affected members of the family with ARS that causes an amino acid substitution from tryptophan to cysteine at codon 86. CONCLUSIONS: We found a novel p.W86C mutation in PITX2 in a Chinese family with ARS. The tryptophan residue at position 86 is strictly conserved in PITX2a proteins from several species and in homeodomain proteins. We suggest that this mutation in PITX2 is the cause of typical ARS in patients. Our results may be useful for better understanding of the spectrum of PITX2 mutations and the role of PITX2 in the development and progression of ARS.

SUBMITTER: Li D

PROVIDER: S-EPMC2592999 | biostudies-literature | 2008

REPOSITORIES: biostudies-literature

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A novel PITX2 mutation in a Chinese family with Axenfeld-Rieger syndrome.

Li Dandan D Zhu Qingguo Q Lin Hui H Zhou Nan N Qi Yanhua Y

Molecular vision 20081205

<h4>Purpose</h4>Axenfeld-Rieger syndrome (ARS) is an autosomal dominant disorder characterized by extraocular anomalies and developmental defects of the anterior segment. PITX2 (paired-like homeodomain transcription factor 2) is considered the major causative gene. In this study, we characterized the molecular defect in PITX2 in a Chinese family with ARS.<h4>Methods</h4>Two generations of the family with ARS were enrolled in the present study. In addition to ophthalmologic examinations, polymera ...[more]

PMID: 19052653

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Project description:Purpose:To identify the genetic cause in a four-generation Chinese family with Axenfeld-Rieger syndrome (ARS). Methods:The family members received clinical examinations of the eye, tooth, periumbilical skin, and heart. Sanger sequencing and whole-exome sequencing (WES) were performed to screen potential mutations. The genomic deletion region around the PITX2 gene was estimated from single nucleotide polymorphism (SNP) data from WES and then confirmed with "quantitative PCR (qPCR) using a set of primers. The DNA breakpoint was further identified with long-range PCR and Sanger sequencing. Results:Symptoms including anterior segment dysplasia of the eye (iris dysplasia, multiple pupils, and posterior embryotoxon), dental dysplasia, and periumbilical skin redundancy were present in all of the affected individuals. Three of them had glaucoma. Corneal abnormalities (inferior sclerocornea, corneal endothelial dystrophy, and central corneal scar) were seen in most of the affected individuals. Cataract, limited eye movement, electrocardiographic abnormalities, intellectual disability, and recurrent miscarriages were observed in some of the affected individuals. No mutations in the coding and exon-intron adjacent regions of the PITX2 and FOXC1 genes were identified with Sanger sequencing. According to the SNP data from WES, we suspected that there might be a deletion region (at most 1.6 Mb) around the PITX2 gene. With the use of qPCR and long-range PCR, we identified a 53,840 bp deletion (chr4: 111,535,454-111,588,933) spanning PITX2 and PANCR. The genomic deletion cosegregated with the major ARS symptoms observed in the family members. Conclusions:With the help of WES, qPCR, and long-range PCR, we identified a genomic deletion encompassing PITX2 and the adjacent noncoding gene PANCR in a Chinese family with ARS. The clinical features of the affected individuals are reported. This work may broaden understanding of the phenotypic and mutational spectrums related to ARS.

Project description:PurposeThe 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.MethodsTwenty-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.ResultsSequence 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.ConclusionsThese 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.

Dataset Information

A novel PITX2 mutation in a Chinese family with Axenfeld-Rieger syndrome.

Publications

A novel PITX2 mutation in a Chinese family with Axenfeld-Rieger syndrome.

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