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Biallelic mutation of protocadherin-21 (PCDH21) causes retinal degeneration in humans.

ABSTRACT: PURPOSE: To describe the clinical findings and mutations in affected members of two families with an autosomal recessive retinal dystrophy associated with mutations in the protocadherin-21 (PCDH21) gene. METHODS: A full genome scan of members of two consanguineous families segregating an autosomal recessive retinal dystrophy was performed and regions identical by descent identified. Positional candidate genes were identified and sequenced. All patients had a detailed ophthalmic examination, including electroretinography and retinal imaging. RESULTS: Affected members of both families showed identical homozygosity for an overlapping region of chromosome 10q. Sequencing of a candidate gene, PCDH21, showed two separate homozygous single-base deletions, c.337delG (p.G113AfsX1) and c.1459delG (p.G487GfsX20), which were not detected in 282 control chromosomes. Affected members of the two families first reported nyctalopia in late teenage years and retained good central vision until their late 30s. No color vision was detected in any proband. The fundus appearance included the later development of characteristic circular patches of pigment epithelial atrophy at the macula and in the peripheral retina. CONCLUSIONS: Biallelic mutations in the photoreceptor-specific gene PCDH21 cause recessive retinal degeneration in humans.

SUBMITTER: Henderson RH

PROVIDER: S-EPMC2806159 | biostudies-literature | 2010

REPOSITORIES: biostudies-literature

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Biallelic mutation of protocadherin-21 (PCDH21) causes retinal degeneration in humans.

Henderson Robert H RH Li Zheng Z Abd El Aziz Mai M MM Mackay Donna S DS Eljinini Mohammad A MA Zeidan Marwan M Moore Anthony T AT Bhattacharya Shomi S SS Webster Andrew R AR

Molecular vision 20100115

<h4>Purpose</h4>To describe the clinical findings and mutations in affected members of two families with an autosomal recessive retinal dystrophy associated with mutations in the protocadherin-21 (PCDH21) gene.<h4>Methods</h4>A full genome scan of members of two consanguineous families segregating an autosomal recessive retinal dystrophy was performed and regions identical by descent identified. Positional candidate genes were identified and sequenced. All patients had a detailed ophthalmic exam ...[more]

PMID: 20087419

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Project description:PurposeTo characterize an N-ethyl-N-nitrosourea-induced dominant mouse mutant, M-1156, that exhibits progressive retinal degeneration and to investigate the pathogenesis of the retinal phenotype in the mutant.MethodsA positional candidate gene approach was used to identify the causative gene in the M-1156 mutant. Funduscopic examination, light microscopy, transmission electron microscopy, and electroretinography were performed to analyze the M-1156 phenotype. Real-time quantitative PCR, immunohistochemistry, and western blotting were also performed.ResultsLinkage analysis enabled the mutant gene to be mapped to a region of chromosome 19 containing Rom1, which encodes rod outer segment membrane protein 1. Sequence analysis demonstrated that the mutation consisted of a single base T-->C substitution at position 1,195 in Rom1 (M96760, National Center for Biotechnology Information [NCBI]) and that the mutant allele was expressed. A putative missense mutation designated Rom1(Rgsc1156) that was identified in the M-1156 mutant mouse causes a Trp to Arg substitution at position 182 in the translated protein. Rom1(Rgsc1156) heterozygotes were found to have a mottled retina and narrowed arteries in the fundus oculi. Photomicrographs of the retina revealed significant differences among the genotypes in the thickness of the outer nuclear layer and in the length of the outer segments of the photoreceptors. The alterations were more marked in the homozygotes than in the heterozygotes. Electron micrographs showed that the diameters of the discs varied in the heterozygotes and that the discs were more compactly stacked than in the wild type. There were significant differences among the genotypes in the amplitude of the a-wave in single-flash electroretinograms, but there were no significant differences among the photopic electroretinograms. Real-time quantitative PCR showed that there were no significant differences among the genotypes in Rom1 or peripherin/rds (Prph2) mRNA levels relative to the rhodopsin (Rho) mRNA level. Rom1 and Prph2 immunoreactivity were decreased in the retinas of the Rom1(Rgsc1156) mutants. Semiquantitative western blot analysis of retinas from 3-week-old Rom1(Rgsc1156) mutants demonstrated significant decreases in Rom1, Prph2, and Rho protein levels in all of the genotypes.ConclusionsThe Trp182Arg substitution in Rom1(Rgsc1156) mutants causes retinal degeneration. The results suggested that Trp182Arg mutant Rom1 causes a decrease in the levels of wild-type Prph2 and Rom1, which in turn cause a reduction in the level of Prph2 containing tetramers in the disc rim region and ultimately result in unstable, disorganized outer segments and photoreceptor degeneration.

Dataset Information

Biallelic mutation of protocadherin-21 (PCDH21) causes retinal degeneration in humans.

Publications

Biallelic mutation of protocadherin-21 (PCDH21) causes retinal degeneration in humans.

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