Progressive Retinal Atrophy, Rod-Cone Dysplasia 3
Affected Genes: PDE6A
Inheritance: Autosomal Recessive
Variant(canFam6):
chr4:58911125: G>DEL
Breed: Cardigan Welsh Corgi
Chinese Crested
Pembroke Welsh Corgi
Pomeranian
Pomsky
General Information: Progressive Retinal Atrophy, Rod-Cone Dysplasia 3 (PRA-rcd3) begins affecting dogs as early as four weeks old, with rapid degeneration of both rod and cone photoreceptor cells in the retina, essential for vision in low and bright light conditions respectively. Symptoms start with abnormal changes in the tapetum—a reflective layer behind the retina—detectable via veterinary eye examinations by six weeks. Initial signs include a loss of peripheral and night vision due to rod cell degeneration, progressing to complete blindness once the cone cells also deteriorate, typically by one year of age. Some dogs may retain limited vision until three or four years old, but the condition invariably leads to total blindness.
How to Read Your Dog's Test Results for this Genetic Variant:
Two Variants Detected: Dog Likely Affected
One Variant Detected: Dog Unlikely Affected
No Variants Detected: No Effect
Gene / Testing Information: Genetic testing for the PDE6A gene helps identify carriers of Progressive Retinal Atrophy, Rod-Cone Dysplasia 3 (PRA-rcd3), providing crucial information for breeders. This condition is autosomal recessive, requiring that a dog inherit two copies of the mutated gene—one from each parent—to exhibit symptoms. Carriers, with only one copy of the mutation, show no symptoms but can pass the gene to offspring. Breeding two carriers results in a 25% chance of producing affected puppies and a 50% chance of producing another carrier. It is essential to test breeding dogs to prevent the propagation of this mutation and reduce the incidence of PRA-rcd3 in the population. Breeders are advised against mating carriers together to avoid birthing affected puppies. Dogs not carrying the mutation are not at risk of producing affected offspring. Nevertheless, due to multiple PRA forms and other genetic diseases, a negative test for PDE6A does not completely rule out other potential genetic conditions.
References:
Corrigendum. Vet Ophthalmol. 2014 Jul;17(4):309-10. Donner J, Kaukonen M, Anderson H, Moller F, Kyostila K, Sankari S, Hytonen M, Giger U, Lohi H. Genetic Panel Screening of Nearly 100 Mutations Reveals New Insights into the Breed Distribution of Risk Variants for Canine Hereditary Disorders. PLoS One 2016 11(8):e0161005.
Downs LM, Hitti R, Pregnolato S, Mellersh CS. Genetic screening for PRA-associated mutations in multiple dog breeds shows that PRA is heterogeneous within and between breeds. Vet Ophthalmol. 2014 17(2):126-130.
Keep JM. Clinical aspects of progressive retinal atrophy in the cardigan Welsh corgi. Aust Vet J. 1972 48(4):197-199.
Petersen-Jones SM, Entz DD, Sargan DR. cGMP phosphodiesterase-alpha mutation causes progressive retinal atrophy in the Cardigan Welsh corgi dog. Invest Ophthalmol Vis Sci. 1999 40(8):1637-1644.
Petersen-Jones SM, Entz DD. 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. Vet Ophthalmol. 2002 5(2):103-106.
Petersen-Jones SM, Zhu FX. Development and use of a polymerase chain reaction-based diagnostic test for the causal mutation of progressive retinal atrophy in Cardigan Welsh Corgis. Am J Vet Res. 2000 61(7):844-846.
Tuntivanich N, Pittler SJ, Fischer AJ, Omar G, Kiupel M, Weber A, Yao S, Steibel JP, Khan NW, Petersen-Jones SM. Characterization of a canine model of autosomal recessive retinitis pigmentosa due to a PDE6A mutation. Invest Ophthalmol Vis Sci. 2009 50(2):801-813.