The aim of the study was to develop an improved test to detect the
codon 616 gene mutation in the alpha
cyclic GMP phosphodiesterase gene that causes progressive
retinal atrophy in the Cardigan Welsh Corgi. We studied 10 control dogs of known genotype at
codon 616 of the alpha
cyclic GMP phosphodiesterase gene and 80 Cardigan Welsh Corgis of unknown genotype. A polymerase chain reaction (PCR) utilizing a mismatched primer was designed so that it introduced a HinfI restriction
enzyme digestion site into the PCR product only if the normal gene sequence was present, the restriction site was not introduced if the
codon 616 mutation was present. An additional HinfI site present in the amplified section from both normal and mutant alleles acted as a positive control for restriction
enzyme digestion. The PCR reliably amplified a portion of the alpha
cyclic GMP phosphodiesterase gene spanning the
codon 616 mutation site. Restriction
enzyme digestion with HinfI and analysis on a suitable
agarose gel reliably ascertained the genotype of the control dogs and was used to identify the genotype of a further 80 test dogs. An improved
DNA-based test for detection of the
codon 616 mutation in the alpha
cyclic GMP phosphodiesterase gene that causes progressive
retinal atrophy in the Cardigan Welsh Corgi has been designed. This overcomes potential problems that could be associated with allele-specific PCR tests such as that used previously in a diagnostic test for this gene mutation.