Summary

Retinitis pigmentosa (RP) is a group of inherited disorders in which abnormalities of the photorreceptors or the retinal epithelium (RPE) of the retina lead to progressive visual loss. RP can be inherited in autosomal dominant, autosomal recessive, X-linked mitochondrial and genetically more complex modes. The purpose of the study was to identify genes causing autosomal recessive retinitis pigmentosa. In this study, 50 families showing autosomal recessive model of inheritance were screened for their linkage to the already reported candidate genes/loci by amplifying the STS markers flanking the genes, followed by their genotyping and haplotype analysis. Two of the families PKRP021 and PKRP019 showed linkage to PDE6A gene, which encodes the subunit of cGMP phosphodiesterase, the effector of the phototransduction cascade. One family, PKRP 014 was found linked with CNGB1 gene, whose product is a subunit of the cGMP-gated cation channel. Fundus examination and patients' history revealed typical, symptoms of progressive photoreceptor degeneration. The study identified the carrier status of normal individuals of the families, which is of great help in genetic counseling. The study may be useful for presymptomatic and prenatal diagnosis of this genetic disease. To do this, however, enrollment of new families with RP is required thereby allowing for the identification of causative genes of RP so as to offer preventive measures and novel therapies to affected individuals as well as to understand vision process in a better way.