Breeds Affected: Gordon Setter, Irish Setter, Standard Poodle
Samples Accepted: Blood, Buccal Swabs
Disease Information: Rod-Cone Dystrophy 4, also known as rcd4, is a disease in which the cone and rod cells in the retina degenerate, leading to blindness. It is classified as late-onset, as most dogs are diagnosed after 9 years of age.
Inheritance Information: Rcd4 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/rcd4 The dog is a carrier, and can pass the allele on to approximately 50% of any offspring. If bred to another N/rcd4 carrier, approximately 25% of the offspring will be normal, 50% will be carriers, and 25% will be affected.
rcd4/rcd4 The dog is affected. If bred to a normal animal, 100% of the offspring will be carriers. If bred to an N/rcd4 carrier, 50% of the offspring will be carriers and 50% will be affected.
– Carriers may be bred to normal animals (N/rcd4 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/rcd4 x N/rcd4) is not recommended due to the possibility of 25% of the offspring being affected.
– Affected animals (rcd4/rcd4) should not be used for breeding.
Test Information: This mutation test identifies a single base change in the C2orf71 gene, also known as C17H2orf71. This mutation appears to be causative for 90% of late-onset rcd4 in the Gordon Setter. Approximately 10% of dogs diagnosed with the disorder do not have this mutation; the other causative mutation has not yet been identified.
Downs, L.M., Hitti, R., Pregnolato, S. and Mellersh, C.S. Genetic screening for PRA‐associated mutations in multiple dog breeds shows that PRA is heterogeneous within and between breeds. Veterinary ophthalmology, 17(2):126-130, 2014. Pubmed reference: 24255994. DOI: 10.1111/vop.12122.
Downs, L.M., Bell, J.S., Freeman, J., Hartley, C., Hayward, L.J., Mellersh, C.S.: Late-onset progressive retinal atrophy in the Gordon and Irish Setter breeds is associated with a frameshift mutation in C2orf71. Anim Genet 44:169-77, 2013. Pubmed reference: 22686255. DOI: 10.1111/j.1365-2052.2012.02379.x.
Further information is available at the Online Mendelian Inheritance in Animals website.