Progressive Retinal Atrophy (rcd4-PRA)

Quick Summary

Progressive retinal atrophy rod-cone degeneration 4 (rcd4-PRA) is a heritable condition characterized by late-onset degeneration of photoreceptor cells in the retina, leading to loss of vision and blindness.
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Phenotype: Dogs with late-onset rcd4-PRA typically start showing signs of visual impairment between 5 and 12 years of age, with an average age of onset of 10 years. Vision loss can progress to complete blindness.

Mode of Inheritance: Autosomal recessive

Alleles: N = Normal, PRA = Progressive retinal atrophy (rcd4-PRA)

Breeds appropriate for testing: Gordon Setter, Irish Setter, Irish Red and White Setter, English Setter, Australian Cattle Dog, Tibetan Terrier, Polish Lowland Sheepdog, Small Munsterlander, Standard Poodle and Poodle crosses, French Bulldog, Golden Retriever, Dachshund

Explanation of results:

•   Dogs with N/N genotype will not have this inherited form of progressive retinal atrophy and cannot transmit this variant to their offspring.

•   Dogs with N/PRA genotype will not be affected by this inherited form of progressive retinal atrophy but are carriers. They may transmit this variant to 50% of their offspring. Matings between two carriers are predicted to produce 25% rcd4-PRA-affected puppies.

•   Dogs with PRA/PRA genotypes are expected to develop this form of progressive retinal atrophy and will transmit this variant to all of their offspring.

Price

$50 single test per animal ($5 discount on 3 or more dogs)
$30 as additional test on same animal

Turnaround Time
At least 15 business days; may be delayed beyond 15 business days if sample requires additional testing, or a new sample is requested.
Additional Details

Progressive retinal atrophy (PRA) is a term used to describe a group of inherited disorders of the retina, characterized by progressive retinal degeneration and consequent blindness. More than 20 mutations in various genes have been associated with PRA in dogs.

Progressive retinal atrophy rod-cone degeneration 4 (rcd4-PRA) is a heritable condition caused by a single-base insertion in the C2orf71 gene (c.3149_3150insC) that leads to a frameshift and the production of a shorter protein than normal.

The variant was first identified in PRA-affected Gordon Setters and found to also be present in PRA-affected Irish Setters who did not have the Irish Setter rcd1-PRA mutation. Although this variant explained a majority of PRA-affected Gordon Setter dogs, a few affected dogs did not have this mutation, suggesting that late-onset PRA in Gordon Setters may be caused by more than one genetic variant.

The disorder is characterized by late-onset degeneration of photoreceptor cells in the retina, leading to loss of vision and eventually blindness. Age of onset for rcd4-PRA is quite variable in Gordon Setters and dogs with this disease can start showing signs of visual impairment between 5 and 12 years of age, with an average age of onset of approximately 10 years.

The disease is inherited in an autosomal recessive fashion and two copies are required for an animal to be affected, with both sexes being equally affected. Dogs with one copy of the C2orf71 variant are considered carriers and unaffected. However, breeding two carriers together is expected to produce 25% affected offspring and 50% carriers.

 

Testing recommendations: Testing for rcd4-PRA assists owners and breeders in identifying affected and carrier dogs. Breeders can use results from the test as a tool for selection of mating pairs to avoid producing affected dogs.

Species

Dog

Type of Test

Results Reported As

Test Result

Progressive Retinal Atrophy (rcd4-PRA)

N/N

Normal. Dog does not have the variant associated with rcd4-PRA.

N/PRA

Carrier. Dog has one copy of the variant associated with rcd4-PRA.

PRA/PRA

Affected. Dog has two copies of the variant associated with rcd4-PRA and will likely develop the disease.

References

Downs, L. M., Bell, J. S., Freeman, J., Hartley, C., Hayward, L. J., & Mellersh, C. S. (2013). Late-onset progressive retinal atrophy in the Gordon and Irish Setter breeds is associated with a frameshift mutation in C2orf71. Animal genetics44(2), 169–177. https://doi.org/10.1111/j.1365-2052.2012.02379.x