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A novel mutation in GRK1 causes Oguchi disease in a consanguineous Pakistani family.

Azam M, Collin RW, Khan MI, Shah ST, Qureshi N, Ajmal M, den Hollander AI, Qamar R, Cremers FP - Mol. Vis. (2009)

Bottom Line: Fine-mapping of a common homozygous region on chromosome 13q was performed using fluorescent microsatellite markers.This mutation is predicted to result in premature termination of the protein product, thereby affecting the phototransduction cascade.This mutation segregated in eight affected members.

View Article: PubMed Central - PubMed

Affiliation: Department of Biosciences, COMSATS Institute of Information Technology, Islamabad, Pakistan.

ABSTRACT

Purpose: The purpose of this study was to identify the underlying molecular genetic defect in a large consanguineous Pakistani family with Oguchi disease who had been given a diagnosis of autosomal recessive retinitis pigmentosa.

Methods: The family was genotyped with the Affymetrix 10K single nucleotide polymorphism array. Fine-mapping of a common homozygous region on chromosome 13q was performed using fluorescent microsatellite markers. Mutation analysis was done by direct sequencing of the candidate gene GRK1 located in the region. The segregation of a novel mutation in the family and the frequency of the identified mutation in the Pakistani population were determined by StuI RFLP analysis.

Results: Genetic mapping supported the diagnosis of typical Oguchi disease in a Pakistani family and also resulted in the identification of a novel nonsense mutation (c.614C>A; p.S205X) in exon 1 of GRK1. This mutation is predicted to result in premature termination of the protein product, thereby affecting the phototransduction cascade. A clinical reappraisal of the family revealed that all patients homozygous for this variant had Oguchi disease.

Conclusions: This is the first report to describe a mutation causing typical Oguchi disease in a large consanguineous Pakistani family. This mutation segregated in eight affected members.

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Related in: MedlinePlus

Sequence chromatograms and segregation analysis of the p.S205X GRK1 variant. A: Sequence chromatogram of part of exon 1. Sequence of normal control sample (left panel) and an affected individual IV-1 (right panel) with the homozygous mutant sequence c.614C>A. B: StuI restriction analysis of the 552 bp PCR products of exon 1 in all family members. Fragments were resolved on an 1.5% agarose gel. Individuals with a single fragment of 552 bp were identified as homozygous normal since they did not contain the restriction site for StuI. Those with three fragments (552 bp, 366 bp, and 186 bp) were heterozygous carriers of the mutation, and those with two fragments (366 bp and 186 bp) carried the mutation homozygously.
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f3: Sequence chromatograms and segregation analysis of the p.S205X GRK1 variant. A: Sequence chromatogram of part of exon 1. Sequence of normal control sample (left panel) and an affected individual IV-1 (right panel) with the homozygous mutant sequence c.614C>A. B: StuI restriction analysis of the 552 bp PCR products of exon 1 in all family members. Fragments were resolved on an 1.5% agarose gel. Individuals with a single fragment of 552 bp were identified as homozygous normal since they did not contain the restriction site for StuI. Those with three fragments (552 bp, 366 bp, and 186 bp) were heterozygous carriers of the mutation, and those with two fragments (366 bp and 186 bp) carried the mutation homozygously.

Mentions: One of the genes residing in the homozygous interval was GRK1 (at 113.3 Mb), in which mutations have been reported [10] to cause Oguchi disease. All seven coding exons and flanking intronic sequences of GRK1 were sequenced in affected family members IV-1, V-5, and V-11. Sequencing revealed a homozygous change of nucleotide C>A at position 614 in exon 1 of the GRK1 gene in these three patients. This nucleotide change results in a nonsense mutation, p.S205X (Figure 3A).


A novel mutation in GRK1 causes Oguchi disease in a consanguineous Pakistani family.

Azam M, Collin RW, Khan MI, Shah ST, Qureshi N, Ajmal M, den Hollander AI, Qamar R, Cremers FP - Mol. Vis. (2009)

Sequence chromatograms and segregation analysis of the p.S205X GRK1 variant. A: Sequence chromatogram of part of exon 1. Sequence of normal control sample (left panel) and an affected individual IV-1 (right panel) with the homozygous mutant sequence c.614C>A. B: StuI restriction analysis of the 552 bp PCR products of exon 1 in all family members. Fragments were resolved on an 1.5% agarose gel. Individuals with a single fragment of 552 bp were identified as homozygous normal since they did not contain the restriction site for StuI. Those with three fragments (552 bp, 366 bp, and 186 bp) were heterozygous carriers of the mutation, and those with two fragments (366 bp and 186 bp) carried the mutation homozygously.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2742643&req=5

f3: Sequence chromatograms and segregation analysis of the p.S205X GRK1 variant. A: Sequence chromatogram of part of exon 1. Sequence of normal control sample (left panel) and an affected individual IV-1 (right panel) with the homozygous mutant sequence c.614C>A. B: StuI restriction analysis of the 552 bp PCR products of exon 1 in all family members. Fragments were resolved on an 1.5% agarose gel. Individuals with a single fragment of 552 bp were identified as homozygous normal since they did not contain the restriction site for StuI. Those with three fragments (552 bp, 366 bp, and 186 bp) were heterozygous carriers of the mutation, and those with two fragments (366 bp and 186 bp) carried the mutation homozygously.
Mentions: One of the genes residing in the homozygous interval was GRK1 (at 113.3 Mb), in which mutations have been reported [10] to cause Oguchi disease. All seven coding exons and flanking intronic sequences of GRK1 were sequenced in affected family members IV-1, V-5, and V-11. Sequencing revealed a homozygous change of nucleotide C>A at position 614 in exon 1 of the GRK1 gene in these three patients. This nucleotide change results in a nonsense mutation, p.S205X (Figure 3A).

Bottom Line: Fine-mapping of a common homozygous region on chromosome 13q was performed using fluorescent microsatellite markers.This mutation is predicted to result in premature termination of the protein product, thereby affecting the phototransduction cascade.This mutation segregated in eight affected members.

View Article: PubMed Central - PubMed

Affiliation: Department of Biosciences, COMSATS Institute of Information Technology, Islamabad, Pakistan.

ABSTRACT

Purpose: The purpose of this study was to identify the underlying molecular genetic defect in a large consanguineous Pakistani family with Oguchi disease who had been given a diagnosis of autosomal recessive retinitis pigmentosa.

Methods: The family was genotyped with the Affymetrix 10K single nucleotide polymorphism array. Fine-mapping of a common homozygous region on chromosome 13q was performed using fluorescent microsatellite markers. Mutation analysis was done by direct sequencing of the candidate gene GRK1 located in the region. The segregation of a novel mutation in the family and the frequency of the identified mutation in the Pakistani population were determined by StuI RFLP analysis.

Results: Genetic mapping supported the diagnosis of typical Oguchi disease in a Pakistani family and also resulted in the identification of a novel nonsense mutation (c.614C>A; p.S205X) in exon 1 of GRK1. This mutation is predicted to result in premature termination of the protein product, thereby affecting the phototransduction cascade. A clinical reappraisal of the family revealed that all patients homozygous for this variant had Oguchi disease.

Conclusions: This is the first report to describe a mutation causing typical Oguchi disease in a large consanguineous Pakistani family. This mutation segregated in eight affected members.

Show MeSH
Related in: MedlinePlus