Progressive Retinal Atrophy, Cone-Rod Dystrophy 3 (Glen of Imaal Terrier Type)
Affected Genes: ADAM9
Inheritance: Autosomal Recessive
Variant(canFam6):
chr16:26952773-26993546: 40 kb deletion
Breed: Glen of Imaal Terrier
General Information: Progressive Retinal Atrophy, Cone-Rod Dystrophy 3 (PRA-crd3) is a genetic condition that affects the eyes of Glen of Imaal Terriers, causing gradual degeneration of both rod and cone photoreceptor cells in the retina. These cells are crucial for vision in low light (rods) and bright light (cones). Typically, the first signs of PRA-crd3 appear around 3 years of age, starting with changes in the reflectivity and appearance of the tapetum, a structure behind the retina, as observed in veterinary eye exams. Affected dogs initially experience night blindness and peripheral vision loss between 3 and 5 years of age. Over time, these visual impairments progress to complete 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 PRA-crd3 focuses on the ADAM9 gene in Glen of Imaal Terriers. This condition is inherited in an autosomal recessive manner, meaning a dog must inherit two copies of the mutated gene (one from each parent) to be affected. Carrier dogs, which have one normal and one mutated gene, do not show symptoms but can pass the mutation to their offspring. If two carriers are bred, there is a 25% chance of producing an affected puppy and a 50% chance of producing a carrier. Genetic testing is essential for responsible breeding practices to avoid producing affected pups. By breeding carriers only with dogs that do not carry the mutation, breeders can help eliminate this condition from their lines. It is important to note that even if a dog tests negative for the ADAM9 mutation, they may still be at risk for other forms of progressive retinal atrophy caused by different genetic mutations.
References:
Goldstein O, Mezey JG, Boyko AR, Gao C, Wang W, Bustamante CD, Anguish LJ, Jordan JA, Pearce-Kelling SE, Aguirre GD, Acland GM. An ADAM9 mutation in canine cone-rod dystrophy 3 establishes homology with human cone-rod dystrophy 9. Mol Vis. 2010 16:1549-1569.
Kropatsch R, Petrasch-Parwez E, Seelow D, Schlichting A, Gerding WM, Akkad DA, Epplen JT, Dekomien G. Generalized progressive retinal atrophy in the Irish Glen of Imaal Terrier is associated with a deletion in the ADAM9 gene. Mol Cell Probes 2010 24(6):357-363.