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C. Kannabiran, H. Pal Singh, S. Jalali, R. Narayanan; Linkage of Autosomal Dominant Retinitis Pigmentosa (ADRP) to Chromosome 6q23. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4081.
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To map the disease gene in a large family affected with ADRP.
A three-generation Indian family with ADRP including a total of 35 individuals was recruited based on ophthalmic evaluation. Consent was obtained for collection of blood samples and genetic analyses. Genotyping of selected microsatellite markers was carried out on the ABI3130 XL genetic analyzer. Linkage analysis was performed under an autosomal dominant model with full penetrance using the EasyLinkage package v 5.08. Allele frequencies for relevant markers were determined on a control population of Indian origin.
Affected individuals had night blindness as the initial symptom with progressive visual loss subsequently. Fundus features ranged from mild changes in the RPE to diffuse atrophy of the RPE, retinal pigment migration, vascular attenuation and disc pallor. Nine members ranging from ages of 16-65 yrs, were affected with typical fundus features and loss of vision and/or ERG responses. In six additional individuals of age range 9-30 yrs, the disease was mild with no visual loss and slight changes in the RPE. Genotyping and linkage analysis were carried out for 28 markers selected from the ABI panels for their proximity to known retinal dystrophy loci. A maximum LOD score of 3.2 was obtained for marker D6S262 on chromosome 6q23. Seven additional markers spanning a region of ~45 cM on chromosome 6q23 were subsequently genotyped. Haplotype analysis revealed an interval of ~15 cM between D6S287 and D6S270 common to affected individuals in the family. There are no known candidate genes for RP in this region.
The ADRP locus at chromosome 6q23 in this family may represent a novel locus and does not include any of the genes known till date to cause RP within the mapped interval.
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