The Cys214-->Ser Mutation in Peripherin/rds Causes a Loss-of-function Phenotype in Transgenic Mice

P/rds (peripherin/retinal degeneration slow) is a photoreceptor-specific membrane glycoprotein necessary for outer segment disc morphogenesis. Mutations in P/rds are associated with different blinding diseases. A C214S (Cys214-->Ser) missense mutation has been shown to be the cause for a late-onset form of ADRP (autosomal dominant retinitis pigmentosa) in humans. In the present study, we generated transgenic mice expressing P/rds with the C214S mutation and crossed them into rds mutant mice to elucidate the mechanism underlying the pathology of ADRP. Although an ample amount of transgene message was formed in C214S retinas from all transgenic lines, only a trace amount of the mutant protein was detected by Western blotting and immunoprecipitation. C214S mice on the wild-type or rds+/- backgrounds exhibited no signs of negative effects of the mutation on retinal structure or function, suggesting a loss-of-function phenotype. This phenotype is further supported by the absence of outer segment formation in the C214S mice on the rds-/- background. In contrast, expression of C214S protein in the inner retinal cells of transgenic mice or in COS cells resulted in the formation of a substantial amount of mutant protein, signifying a possible photoreceptor-specific regulation of P/rds. These results provide evidence that the loss-of-function phenotype seen in C214S transgenic mice shows a disease progression that correlates with ADRP patients carrying the same mutation, indicating that the C214S mutation on one allele of P/rds results in haploinsufficiency.