Development and use of a polymerase chain reaction-based diagnostic test for the causal mutation of progressive retinal atrophy in Cardigan Welsh Corgis

OBJECTIVE: To develop an allele-specific polymerase chain reaction (ASPCR)-based diagnostic test for the mutation in the cyclic guanosine monophosphate phosphodiesterase alpha subunit gene (PDE6A) that causes the rcd3 form of progressive retinal atrophy (PRA) in Cardigan Welsh Corgis. ANIMALS: 1 affected homozygote, 1 unaffected carrier, 1 genotypically normal dog, and 500 unknown-PRA status Cardigan Welsh Corgis. PROCEDURE: Control blood samples were collected from Cardigan Welsh Corgis of known PRA status (ie, affected homozygote, unaffected carrier, and a genotypically normal dog) for test development. Test blood samples were collected from 500 Cardigan Welsh Corgis of unknown PRA status. Genomic DNA was used as a template in ASPCR. One pair of primers was designed to specifically amplify only the mutant allele, and another set to amplify only the wildtype allele. The PCR conditions were adjusted to ensure each reaction was 100% specific. RESULTS: The PCR conditions were identified so that each ASPCR only amplified the allele it was designed to amplify. Of the 500 Cardigan Welsh Corgis tested using the newly developed ASPCR, 457 were homozygous for the normal allele (genotypically normal), 43 were heterozygous (phenotypically normal carriers), and none were homozygous for the mutant allele. CONCLUSION AND CLINICAL RELEVANCE: A rapid, ASPCR diagnostic test able to detect the PDE6A gene mutation responsible for the rcd3 form of PRA in Cardigan Welsh Corgis was developed. The test provides a useful service for Cardigan Welsh Corgi breeders and will enable them to prevent the birth of homozygote mutant dogs.     

Genetic screening for progressive retinal atrophy in the Australian population of Irish Setters

OBJECTIVE: To determine whether the rcd-1 mutation causing progressive retinal atrophy (PRA) in Irish Setters is in the Australian breeding population. METHOD: DNA samples were tested for the mutation using the Polymerase Chain Reaction and specific primer nucleotides to amplify the phosphodiesterase gene followed by restriction enzyme cleavage and fragment size determination. RESULTS: No mutant alleles were found in 38 Irish Setters, representing over 80% of all major breeding stock in five Australian states. CONCLUSIONS: It is likely that the Australian population of Irish Setters is free of the rcd-1 form of PRA.