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Progressive Retinal Atrophy, Golden Retriever 2

Progressive Retinal Atrophy, Golden Retriever 2 (GR-PRA2) is a late-onset inherited eye disease in Golden Retrievers, causing gradual vision loss and eventual blindness.

Affected Genes: TTC8

Inheritance: Autosomal Recessive

Variant(canFam6):
chr8:59669523: 1 bp deletion A

Breed: Australian Labradoodle
Golden Retriever
Goldendoodle
Lab/Golden Cross
Labradoodle
Labrador Retriever
Service/Assistance Golden Retriever
Service/Assistance Lab/Golden Retriever cross
Service/Assistance Labrador Retriever
UK Breed Council Labrador Retriever

General Information: Progressive Retinal Atrophy, Golden Retriever 2 (GR-PRA2), is a late-onset inherited eye disease that leads to the gradual degeneration of the retina, resulting in progressive vision loss and eventual blindness in affected dogs. Typically, Golden Retrievers with GR-PRA2 begin showing symptoms around 4 to 5 years of age, though the onset can vary. Early signs include changes in the reflectivity and appearance of the tapetum, a structure behind the retina, which can be detected during a veterinary eye exam. As the disease progresses, affected dogs experience thinning of the retinal blood vessels, leading to decreased blood flow to the retina. Initial clinical signs include night blindness and loss of peripheral vision, which gradually deteriorates to total blindness. In addition to retinal degeneration, dogs with GR-PRA2 may exhibit other symptoms resembling Bardet-Biedl syndrome in humans, such as cataracts, obesity, abnormal facial features, poor sense of smell, short stature, and various reproductive issues. These additional symptoms vary in severity among affected dogs, and each may present a unique combination of clinical signs.

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 TTC8 gene is crucial for identifying carriers of the mutation responsible for Progressive Retinal Atrophy, Golden Retriever 2 (GR-PRA2). This condition is inherited in an autosomal recessive manner, meaning that a dog must inherit two copies of the mutated gene, one from each parent, to develop the disease. Carrier dogs, which have only one copy of the mutation, typically do not exhibit symptoms but can pass the gene to their offspring. When two carriers are bred, each puppy has a 25% chance of developing GR-PRA2 and a 50% chance of being a carrier. Genetic testing is essential for responsible breeding practices, as it allows breeders to identify and avoid mating two carriers, thereby reducing the risk of producing affected puppies. By ensuring that only non-carrier dogs are bred, breeders can help eliminate this debilitating condition from Golden Retriever lines, leading to healthier future generations. It is important to note that while a normal result for the TTC8 gene reduces the risk for GR-PRA2, it does not exclude the possibility of other types of progressive retinal atrophy caused by mutations in different genes, necessitating comprehensive genetic screening for full assurance.

References:
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.

Downs LM, Wallin-Håkansson B, Bergström T, Mellersh CS. A novel mutation in TTC8 is associated with progressive retinal atrophy in the golden retriever. Canine Genet Epidemiol. 2014 1:4.

Makelainen S, Hellsand M, van der Heiden AD, Andersson E, Thorsson E, Holst BS, Haggstrom J, Ljungvall I, Mellersh C, Hallbrook F, Andersson G, Ekesten B, Bergstrom TF. Deletion in the Bardet–Biedl Syndrome Gene TTC8 Results in a Syndromic Retinal Degeneration in Dogs.Genes (Basel) 2020 11(9):1090.