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)-b ased 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 o f known PRA status (ie, affected homozygote, unaffected carrier, and a geno typically normal dog) for test development. Test blood samples were collect ed from 500 Cardigan Welsh Corgis of unknown PRA status. Genomic DNA was us ed 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 wildty pe allele. The PCR conditions were adjusted to ensure each reaction was 100 % specific. Results-The PCR conditions were identified so that each ASPCR only amplifie d the allele it was designed to amplify. Of the 500 Cardigan Welsh Corgis t ested using the newly developed ASPCR, 457 were homozygous for the normal a llele (genotypically normal), 43 were heterozygous (phenotypically normal c arriers), and none were homozygous for the mutant allele. Conclusion and Clinical Relevance-A rapid, ASPCR diagnostic test able to de tect the PDE6A gene mutation responsible for the rcd3 form of PRA in Cardig an Welsh Corgis was developed. The test provides a useful service for Cardi gan Welsh Corgi breeders and will enable them to prevent the birth of homoz ygote mutant dogs.