UC Davis School of Veterinary Medicine Veterinary Genetics Laboratory

Golden Retriever Progressive Retinal Atrophy
(GR_PRA1 and GR_PRA2)

Introduction

More than 20 mutations have been identified that result in canine Progressive Retinal Atrophy (PRA). The condition is characterized by bilateral degeneration of the retina resulting in progressive vision loss leading to total blindness. Golden Retrievers are affected by more than one form of PRA with mutations in three distinct genes having been identified. Two of such mutations are known as GR_PRA1 and GR_PRA2. GR_PRA1 results from a mutation in the SLC4A3 gene and accounts for over 60% of diagnosed Golden Retrievers. GR_PRA2 results from a mutation in the TTC8 gene and accounts for 30% of Golden Retrievers diagnosed with PRA. Both mutations are autosomal recessive thus two copies of the same affected gene must be present for the disease to be observed and both males and females are equally affected. Presence of one copy of each affected gene in the same dog will not cause blindness. Clinical signs of GR_PRA1 appear around 6 years of age. Clinical symptoms of GR-PRA2 appear around 4 years of age. Breeding two carriers with the same mutation is predicted to produce 25% affected puppies and 50% carriers. Mating a carrier of GR_PRA1 with a carrier of GR_PRA2 will not produce affected animals.

The VGL offers a test for GR_PRA1 and 2 to assist owners and breeders in identifying affected and carrier dogs. The test uses DNA collected from buccal (cheek) swabs, thus avoiding blood sample collection. Breeders can use results from the tests as a tool for selection of mating pairs to avoid producing affected dogs. Genetic testing for GR_PRA1 and 2 is recommended for Golden Retrievers and Golden Doodles. GR-PRA2 has been reported at low frequency in Labrador Retrievers but an extensive survey of the US population has yet to be investigated.

 

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Results reported as:

GR_PRA1
N/N No copies of the GR_PRA1 mutation present; dog is normal.
N/GR_PRA1 1 copy of the GR_PRA1 mutation; dog is normal but is a carrier.
GR_PRA1/ GR_PRA1 2 copies of the GR_PRA1 mutation; dog is affected.

 

GR_PRA2
N/N No copies of the GR_PRA2 mutation; dog is normal.
N/GR_PRA2 1 copy of the GR_PRA2 mutation; dog is normal but is a carrier.
GR_PRA2/ GR_PRA2 2 copies of the GR_PRA2 mutation; dog is affected.

Note: The GR_PRA2 test is performed under license through Animal Health Trust, Newmarket, England. VGL is not authorized to offer this test in Europe.

References:

Downs LM, Wallin-Håkansson B, Boursnell M, Marklund S, Hedhammar Å, Truvé K, Hübinette L, Lindblad-Toh K, Bergström T, Mellersh CS. 2011. A frameshift mutation in golden retriever dogs with progressive retinal atrophy endorses SLC4A3 as a candidate gene for human retinal degenerations. PLoS One 6(6):e21452

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

 
Veterinary Genetics Laboratory, Tel 530-752-2211, Email VGL