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Progressive Retinal Atrophy, Rod-Cone Dysplasia 4

Other Names: PRA-rcd4
Affected Genes: C2orf71
Inheritance: Autosomal Recessive
Mutation: chr17:22907388-22907389: 1 bp insertion (ins C)
Breed(s): Australian Cattle Dog, Australian Stumpy Tail Cattle Dog, English Setter, Goldendoodle, Gordon Setter, Irish Red and White Setter, Irish Setter, Japanese Spitz, Labradoodle, Llewelyn Setter, Miniature Poodle, Old Danish Pointer, Polish Lowland Sheepdog, Poodle, Small Munsterlander , Standard Poodle, Tibetan Terrier, Toy Poodle

Common Symptoms

Progressive retinal Atrophy, Rod-cone dysplasia 4 (PRA-RCD4) is a late-onset inherited eye disease affecting dogs. Affected dogs begin showing clinical symptoms related to retinal degeneration between 7 to 12 years of age. Initial clinical signs of progressive retinal atrophy involve changes in reflectivity and appearance of a structure behind the Retina called the Tapetum that can be observed on a veterinary eye exam. Progression of the disease leads to thinning of the retinal blood vessels, signifying decreased blood flow to the retina. Affected dogs initially have vision loss in dim light (night blindness) and loss of peripheral vision, eventually progressing to complete blindness in most affected dogs.

Testing Tips

Genetic testing of the C2ORF71 gene will reliably determine whether a dog is a genetic Carrier of PRA-RCD4. PRA-RCD4 is inherited in an Autosomal Recessive manner in dogs meaning that they must receive two copies of the mutated gene (one from each parent) to develop the disease. In general, carrier dogs do not have features of the disease but when bred with another carrier of the same Mutation, there is a risk of having affected pups. Each pup that is born to this pairing has a 25% chance of inheriting the disease and a 50% chance of inheriting one copy and being a carrier of the C2ORF71 gene mutation. Reliable genetic testing is important for determining breeding practices. Because symptoms do not appear until adulthood, genetic testing should be performed before breeding. In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of known carriers to each other is not recommended. Dogs that are not found to have this specific mutation have no increased risk of having affected pups. However, because there are multiple types of progressive retinal Atrophy caused by mutations in other genes, a normal result in C2ORF71 does not exclude progressive retinal atrophy in a pedigree.

There may be other causes of this condition in dogs and a normal result does not exclude a different mutation in this gene or any other gene that may result in a similar genetic disease or trait.

References

  • Djajadiningrat-Laanen SC, Boevé MH, Stades FC, van Oost BA. Familial non-rcd1 generalised retinal degeneration in Irish setters. J Small Anim Pract. 2003 Mar;44(3):113-6. [PubMed: 12653325]
  • Downs LM, Bell JS, Freeman J, Hartley C, Hayward LJ, Mellersh CS. Late-onset progressive retinal atrophy in the Gordon and Irish Setter breeds is associated with a frameshift mutation in C2orf71. Anim Genet. 2013 Apr;44(2):169-77. [PubMed: 22686255]
  • Downs LM, Hitti R, Pregnolato S, Mellersh CS. Genetic screening for PRA-associated mutations in multiple dog breeds shows that PRA is heterogeneous within and between breeds. Vet Ophthalmol. 2014 Mar;17(2):126-30. [PubMed: 24255994]
  • Miyadera K, Acland GM, Aguirre GD. Genetic and phenotypic variations of inherited retinal diseases in dogs: the power of within- and across-breed studies. Mamm Genome. 2012 Feb; 23(1-2):40-61. [PubMed: 22065099]
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