Genetic basis - GR-PRA2 is caused by a mutation in the TTC8 gene (also known as BBS8), involved in photoreceptor function. The mutation is a deletion (c.669delA) in exon 8 of the TTC8 gene. Inheritance pattern is autosomal recessive: two copies of the mutation (pra2/pra2) are required for disease expression. Carriers (N/pra2) are clinically normal but can pass the mutated gene to offspring.
Pathophysiology - The disease causes progressive photoreceptor cell degeneration in the retina, leading to loss of vision. It is similar to Retinitis Pigmentosa in humans and affects both rod and cone cells. Vision loss typically begins around 4 years of age, progressing to complete blindness. The retinal degeneration is gradual but irreversible.
Complications - Initial symptom is night blindness, followed by loss of day and color vision. Complete vision loss significantly impairs quality of life, requiring adaptations. No effective cure; treatment is supportive.
Why This Matters to Breeders and Vets - Genetic testing enables breeders to prevent producing blind puppies and reduce disease frequency. Vets can provide accurate diagnosis and prognosis based on genotype and develop appropriate management plans. Maintains the health, welfare, and quality of life of Golden Retrievers. Supports informed decision-making and responsible breeding programs.