Evaluation of RDS/Peripherin and ROM1 as candidate genes in generalised progressive retinal atrophy and exclusion of digenic inheritance

Abstract

Generalised progressive retinal atrophy (gPRA) is a heterogeneous group of hereditary diseases causing degeneration of the retina in dogs and cats. As a combination of mutations in the RDS/Peripherin and the ROM1 genes leads to the phenotype of retinitis pigmentosa in man we first performed mutation analysis to screen these genes for disease causing mutations followed by the investigation of a digenic inheritance in dogs. We cloned the RDS/Peripherin gene and investigated the RDS/Peripherin and ROM1 genes for disease causing mutations in 13 gPRA-affected dog breeds including healthy animals, obligate gPRA carriers and gPRA-affected dogs. We screened for mutations using single strand conformation polymorphism (SSCP) analysis. Sequence analysis revealed several sequence variations. In the coding region of the RDS/Peripherin gene three nucleotide exchanges were identified (A277C; C316T; G1255A), one of which leads to an amino acid substitution (Ala339Thr). Various silent sequence variations were found in the coding region of the ROM1 gene (A536G, G1006A, T1018C, T1111C, C1150T, C1195T), as well as an amino acid substitution (G252T; Ala54Ser). By excluding the respective gene as a cause for gPRA several sequence variations in the intronic regions were investigated. None of these sequence variations cosegregated with autosomal recessively (ar) transmitted gPRA in 11 breeds. The candidate gene RDS/Peripherin obviously does not harbour the critical mutation causing the autosomal recessive form of gPRA because diseased individuals show heterozygous genotypes for sequence variations in the Miniature Poodle, Dachshund, Australian Cattle Dog, Cocker Spaniel, Chesapeake Bay Retriever, Entlebucher Sennenhund, Sloughi, Yorkshire Terrier, Tibet Mastiff, Tibet Terrier and Labrador Retriever breeds. In the following breeds the ROM1 gene was also excluded indirectly for gPRA: Miniature Poodle, Dachshund, Australian Cattle Dog, Sloughi, Collie, Tibet Terrier, Labrador Retriever and Saarloos/Wolfhound. Digenic inheritance for gPRA is practically excluded for both these genes in four breeds: Miniature Poodle, Dachshund, Labrador Retriever and Saarloos/Wolfhound.

Role of Caveolae and Caveolins in Health and Disease

“…RP is generally the result of a single gene defect (monogentic); however, in at least one case, inheritance of defects in two unrelated genes (peripherin/rds and rom-1) appears necessary to cause RP (41, 93,106,141,180,205). While a multitude of genes have now been implicated in the pathogenesis of RP, the role of caveolin-1 is only now being elucidated (93).…”

Indirect exclusion of four candidate genes for generalized progressive retinal atrophy in several breeds of dogs

“…Until now, causal mutations for ar gPRA have been identified exclusively in few dog breeds [3-7]. On the other hand, a number of photoreceptor genes have been excluded as the primary genetic cause of the trait in up to 26 dog breeds [8-15] investigated here.…”

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“…The disease causing mutation is a T4R exchange in the rhodopsin ( RHO ) gene [13]. A number of other retinal genes have been excluded as harbouring mutations for gPRA in several dog breeds: RHO; [14], RDS/peripherin and ROM -1 [15] as well as the α – and γ-subunits of transducin [16] and SAG [17]. Yet, the SAG gene had been analyzed on the exonic level exclusively, i.e.…”