Breeds Affected: Collie
Samples Accepted: Blood, Buccal Swabs
Disease Information: Rod-Cone Dystrophy 2, also known as rcd2, is a disease in which the cone and rod cells in the retina degenerate, leading to blindness. It is classified as early-onset, as clinical signs are normally noticed between 3 – 5 months of age, and results in complete blindness by 7 8 months.
Inheritance Information: Rcd2 is autosomal recessive, meaning that animals with two copies of this allele will be affected. Animals with one copy of the gene will be clinically-normal carriers.
The possible genotypes are:
N/N The dog is normal, and cannot produce affected offspring.
N/rcd2 The dog is a carrier, and can pass the allele on to approximately 50% of any offspring. If bred to another N/rcd2 carrier, approximately 25% of the offspring will be normal, 50% will be carriers, and 25% will be affected.
rcd2/rcd2 The dog is affected. If bred to a normal animal, 100% of the offspring will be carriers. If bred to an N/rcd2 carrier, 50% of the offspring will be carriers and 50% will be affected.
– Carriers may be bred to normal animals (N/rcd2 x N/N) without any risk of producing affected offspring. The offspring should be tested before breeding to determine if they are carriers or normal.
– Breeding two carriers (N/rcd2 x N/rcd2) is not recommended due to the possibility of 25% of the offspring being affected.
– Affected animals (rcd2/rcd2) should not be used for breeding.
Test Information: This mutation test identifies an insertion in the RD3 gene.
Kukekova, AV., Goldstein, O., Johnson, JL., Richardson, MA., Pearce-Kelling, SE., Swaroop, A., Friedman, JS., Aguirre, GD., Acland, GM.: Canine RD3 mutation establishes rod-cone dysplasia type 2 (rcd2) as ortholog of human and murine rd3. Mamm Genome 20:109-23, 2009. Pubmed reference: 19130129. DOI: 10.1007/s00335-008-9163-4.
Further information is available at the Online Mendelian Inheritance in Animals website.