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Progressive Retinal Atrophy Golden Retriever Type 1 (GR-PRA1)
| Acronym: | GR1-PRA, PRA-GR1, GR-PRA1 |
| Gene: | SLC4A3 |
| Mutation: | c.2601_2602insC |
| Inheritance: | Autosomal recessive |
| Sample type: | CHS (Cheek Swab), WBE (Whole Blood EDTA) |
Genetics and characteristics
Progressive retinal atrophy Golden Retriever type 1 (GR1-PRA) is an eye disorder, which belongs to the progressive retinal atrophy group of disorders. Progressive retinal atrophy (PRA) comprises autosomal recessively inherited diseases that lead to degeneration of retinal photoreceptor cells in dogs and other pets. There are more than 20 mutations responsible for specific forms of PRA, and some breeds, including Golden Retrievers, can be affected by more than only one form of PRA. In general, forms of PRA are characterized by disturbance of dark vision, visual field defects, and abnormalities in the electroretinogram. PRA is a progressive disorder and can progress into blindness. The age of onset and rate of retinal degeneration varies between the different forms of the conditions. Vision in dim light and also night vision is possible due to normal functioning rods. PRA causes rode degeneration, which leads to night blindness. The research estimated that PRA causes the death of around 95% of the dog’s photoreceptors. Dog owners or breeders can recognize PRA by ”glow” or ”increased shine” in the eyes. The disease is progressive. The initial stage of PRA is night blindness, while in severe cases advanced stage of PRA causes secondary cataracts or full blindness in the dog. The advanced stage of PRA usually occurs within one year, after the appearance of the first symptoms.
Progressive retinal atrophy Golden Retriever type 1 (GR1-PRA) is a late-onset form of PRA affecting the Labrador retriever breed. The clinical signs occur in affected dogs between 6 to 7 years of age on average, but it can vary among individual dogs. Like other forms of PRA, the first symptoms of progressive retinal atrophy Golden Retriever type 1 (GR1-PRA) are a poor vision in dim light, which eventually progresses into complete blindness. Other than GR1-PRA, there are also other forms of PRA affecting the Golden Retrievers. Those are GR2-PRA and PRA-PRCD, mutation responsible for PRA-PRCD appears to be very rare among the Golden Retriever breed.
The disorder is caused by a non-stop mutation in the SLC4A3 gene. Progressive retinal atrophy Golden Retriever type 1 (GR1-PRA) is inherited as an autosomal recessive disorder and it affects females and males equally. Considering the mutated gene, the dog can be clear, carrier, or affected. Heterozygotes are carriers and they have no symptoms. When mating two carriers, future cubs have a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier. There is no cure for GR1-PRA, and only way to prevent it is to breed dogs that are not carriers of the mutation. Defected genes for autosomal recessive disease can be passed for many generations without affected individuals occurring until two carriers are bred to one another. The only way to find out if there is a chance of getting an affected puppy is to do progressive retinal atrophy Golden retriever type 1 genetic testing.
Results Reported As
Test Result |
Interpretation of test result |
CLEAR |
Tested mutation was not detected in animal with „clear“ result. Animal tested as clear has wild-type allele in homozygous state (i.e. two pairs of healthy alleles). It will not develop disease caused by tested mutation.* It will pass only wild-type allele to its offspring. |
CARRIER |
Tested mutation was detected in animal with „carrier“ result. Animal tested as carrier has one wild-type and one mutation allele, it is in heterozygous state. It will not develop disease caused by tested mutation.* It can pass wild-type or mutation allele to its offspring. |
AFFECTED |
Tested mutation was detected in animal with „affected“ result. Animal tested as affected has two copies of mutation alleles affecting the gene. It is likely the animal will experience a genetic disorder due to this mutation.** It will pass only mutation allele to its offspring. |
*Test excludes only tested mutation but not possible unknown mutations or factors that can lead to similar condition/symptoms.
** Potential unknown mutations or multiple other factors can possibly affect the likelihood of experiencing a genetic disorder.
References:
Downs LM, Wallin-Hakansson B, Boursnell M, Marklund S, Hedhammar A, Truve K, Hubinette L, Lindblad-Toh K, Bergstrom T, Mellersh CS. A frameshift mutation in golden retriever dogs with progressive retinal atrophy endorses SLC4A3 as a candidate gene for human retinal degenerations. PLoS One. 2011;6(6):e21452.