GR-PRA1 - Progressive Retinal Atrophy in Golden Retrievers

Progressive retinal atrophy (PRA) in dogs is the canine equivalent of Retinitis pigmentosa (RP) in humans and is characterized by loss of vision due to degeneration of the photoreceptor cells of the retina.

Various forms of PRA have been identified in more than 100 dog breeds, which were caused by numerous mutation types and exhibit similar clinical signs. However, the aetiology, age of the onset, rate of progression and course of the disease vary between the individual breeds.

Most PRA cases in the Golden Retriever (Golden Retriever - GR) are clinically indistinguishable from other forms of PRA. While the age of diagnosis is most commonly at a relatively late age of approximately 6 years, there is a great deal of variation within the breed. In the closely related Labrador Retriever breed, the only known form of PRA is called progressive rod cone degeneration prcd-PRA. The prcd-PRA has been considered responsible for the loss of vision in at least 22 breeds. However, only a small number of PRA-affected Golden Retrievers have been found to be homozygous for the prcd-mutation.   

In 2011, a new mutation, a single base insertion 2601_2602insC in SLC4A3 gene, responsible for the GR-PRA1 form in Golden Retrievers, was identified (Downs et al, 2011). The SLC4A3 encodes the solute carrier protein that is expressed in the retina. The mutation in this gene causes a shift in the reading frame, formation of non-functional protein necessary for a correct function of photoreceptor cells, resulting in progressive loss of vision.

Except GR-PRA1, golden retrievers can carry also GR-PRA2 and PRA-Prcd - all of these mutations are responsible for developing eye defects. There is still a possibility of existance of other hitherto unknown mutations.

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References:
Downs LM, Wallin-Hakansson B, Boursnell M, Marklund S, Hedhammar A, et al. (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. doi:10.1371/journal.pone.0021452