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O. Goldstein, S. Pearce–Kelling, B. Zengerl, G.M. Acland, G.D. Aguirre; Differentiating prcd and Non–prcd Forms of Canine Adult Onset Autosomal Recessive Hereditary Retinal Degenerations . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3285.
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© ARVO (1962-2015); The Authors (2016-present)
Autosomal recessive, adult onset, hereditary forms of progressive retinal atrophy (PRA) segregate within many canine breeds. In several of these breeds, including American and English Cocker Spaniels, Labrador Retriever, and Miniature and Toy Poodle, the breed–specific diseases are allelic, and cosegregate with the prcd locus on the centromeric end of CFA9, a region homologous to distal HSA17q. For other breeds, however, in which disease clinically similar to prcd segregates, it has not been determined whether the disease is or is not a form of prcd.
To test whether prcd–like diseases, occurring naturally in several canine breeds, are caused by mutations at the prcd locus.
DNA extracted from affected dogs and selected first degree nonaffected relatives was genotyped for a set of SNPs defining the 83 Kb prcd minimal LD interval. In selected cases, privately owned purebred dogs were bred to mixed –breed prcd–affected or –heterozygous colony dogs, and the retinal disease status was evaluated by retinal morphological examination at 16 weeks postnatal, or older.
Test breeding studies resulted in prcd–affected offspring in progeny derived from Australian Cattle Dogs (ACD), Nova Scotia Duck Tolling Retrievers (NSDTR), and Portuguese Water Dogs (PWD). All retinas from progeny derived from test breedings with Basenji, Border Collie (BC), or Italian Greyhound (IG) were morphologically normal. Genotyping data confirmed that the disease in ACDs, NSDTRs and PWDs cosegregated with the prcd–informative SNP haplotype, but that this was not so for Basenji, BC, and IG breeds. SNP haplotyping established prcd as the cause of disease in American Eskimo, Australian Stumpy Tailed Cattle Dog, Chesapeake Bay Retriever, Entlebucher, Finnish Lapphund; and excluded it in Glen of Imaal Terrier, Lhasa Apso, and Papillon breeds. In the Chinese Crested, PRA cosegregated with prcd in some pedigrees, but not others, suggesting that there may be more that one gene causing PRA in this breed.
These studies add to previous understanding of how widespread prcd is in canine populations, and extends the findings to new breeds. This indicates that the prcd mutation must represent a single ancestral mutation, predating the separation of these disparate breeds into isolate populations. As well, it is now certain that adult onset autosomal recessive PRA in some other canine breeds, is not prcd. This creates an opportunity and a challenge to identify these further gene loci.
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