Progressive Retinal Atrophy (PRA) in Irish Setters
Progressive retinal atrophy (PRA) is characterized by degeneration of the retina resulting in progressive vision loss leading to total blindness. In Irish Setters and Irish Red and White Setters, dogs with this disease are typically completely blind before two years of age.
Phenotype: Dogs with this early onset disease are typically completely blind before two years of age with signs often evident by 6 weeks.
Mode of Inheritance: Autosomal recessive
Alleles: N = Normal, PRA = Progressive retinal atrophy (Irish Setter variant)
Breeds appropriate for testing: Irish Setter, Irish Red and White Setter
Explanation of Results:
Dogs with N/N genotype will not have this inherited Irish Setter progressive retinal atrophy and cannot transmit this variant to their offspring.
Dogs with N/PRA genotype are not expected to be affected by this inherited Irish Setter progressive retinal atrophy, but are carriers. They may transmit this variant to 50% of their offspring. Matings between two carriers are predicted to produce 25% of puppies affected by this inherited progressive retinal atrophy.
Dogs with PRA/PRA genotype are predicted to have this inherited Irish Setter progressive retinal atrophy.
Progressive retinal atrophy (PRA) in the Irish Setter and Irish Red and White Setter is an early onset inherited rod-cone dysplasia (type 1-rcd1) resulting from a mutation in phosphodiesterase 6B (PDE6B) enzyme. Dogs with this disease are typically completely blind before two years of age with signs often evident by 6 weeks. The disease is inherited in an autosomal recessive fashion, thus two copies are required for an animal to be affected with both sexes being equally affected. Carrier dogs with one normal and one mutated PDE6B gene are unaffected, but breeding two carriers together is expected to produce 25% affected offspring and 50% carriers.
Testing Irish and Irish Red and White Setters for rcd1-PRA assists owners and breeders in identifying affected and carrier dogs. Breeders can use results from the test as a tool for selection of mating pairs to avoid producing affected dogs.
No copies of the rcd1-PRA mutation. Dog is normal.
1 copy of the rcd1-PRA mutation. Dog is a carrier.
Affected 2 copies of the rcd1-PRA mutation. Dog is affected.
Suber, M.L., Pittler, S.J., Qin, N., Wright, G.C., Holcombe, V., Lee, R.H., Craft, C.M., Lolley, R.N., Baehr, W., & Hurwitz, R.L. (1993). Irish setter dogs affected with rod/cone dysplasia contain a nonsense mutation in the rod cGMP phosphodiesterase beta-subunit gene. Proceedings of the National Academy of Sciences of the United States of America, 90(9), 3968-3972. doi: 10.1073/pnas.90.9.3968