Functional characterization of a novel c.614-622del rhodopsin mutation in a French pedigree with retinitis pigmentosa

PURPOSE To identify and functionally characterize the mutation responsible for autosomal dominant retinitis pigmentosa (adRP) in a large, six-generation French family. METHODS Twenty individuals from this family participated in the genetic investigation. Six affected and 14 unaffected individuals from three-generations were available for linkage analysis using microsatellite markers flanking the rhodopsin (RHO) gene. A two-point logarithm of odds (LOD) score calculation was undertaken using GENEMARKER and MLINK software. Sanger sequencing of RHO was performed. Cellular localization of the mutant protein was performed by transforming SK-N-SH cells with pEGFP-N1-Rho, pEGFP-N1-Rho(P23H), and pEGFP-N1-Rho(c.614-622del). RESULTS The proband had nyctalopia, visual field constriction, peripheral bone spicule pigmentation of the fundus, central acuity (6/24 RE; 6/12 LE) at 55 years of age. Linkage analysis of this family suggested RHO as a possible candidate since the flanking marker D3S1292 yielded a LOD score of 2.43 at θ=0. Cloning of an exon 3 PCR product and direct sequencing of single clones identified a novel deletion in the third exon of RHO, c.614-622del (p.Y206-F208del). The deleted mutant protein localized to the endoplasmic reticulum and formed inclusion bodies. CONCLUSIONS This novel deletion in exon 3 of the RHO gene, c.614-622del results in a classical form of adRP in a multi-generation French family. Protein expression analyses confirmed that the deletion led to protein misfolding and suggest this is a class II mutation, similar to P23H, the most common class II mutation seen in North America.