Isolation of canine retinal arrestin cDNA and exclusion of three candidate genes for Swedish Briard retinal dystrophy

Purpose. Mutations of genes encoding various retina-specific proteins are known to cause a wide spectrum of inherited retinal dystrophies in different species. In the canine, several types of genetic retinal dystrophies have been described affecting primarily the photoreceptors and/or the retinal pigment epithelium. We are performing a systematic analysis of canine candidate genes for such diseases to identify the one mutated in the retinal dystrophy in Swedish Briard dogs. Methods. We isolated and characterised the full length cDNA of canine retinal arrestin by the method of rapid amplification of cDNA ends (RACE). Results. The full length cDNA isolated by us is 1,575 base pairs (bp) long and contains a 1,218 bp-long open reading frame. Conclusions. The homology of the canine arrestin protein is highest with the human analogue (88.9%) and lowest with mouse arrestin (85.3%). The most obvious sequence differences among the different arrestins are in the extreme carboxyl terminus. PCR-SSCP (single strand conformation polymorphism) analysis and direct sequencing of retinal cDNA didn't provide any evidence that mutations in the canine arrestin gene are responsible for the retinal dystrophy seen in the Swedish strain of Briard dogs. Similar data were obtained for the genes encoding rhodopsin and the ß-subunit of photoreceptor-specific phosphodiesterase by segregation analysis.