Breeds Affected: American Staffordshire Terrier
Samples Accepted: Blood, Buccal Swabs
Disease Information: Cone-Rod Dystrophy 1, also known as crd1, is a disease in which the cone and rod cells in the retina degenerate, leading to blindness. Clinical signs can be seen as early as 11 weeks of age, and full blindness results in early adulthood.
Inheritance Information: Crd1 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/crd1 The dog is a carrier, and can pass the allele on to approximately 50% of any offspring. If bred to another N/crd1 carrier, approximately 25% of the offspring will be normal, 50% will be carriers, and 25% will be affected.
crd1/crd1 The dog is affected. If bred to a normal animal, 100% of the offspring will be carriers. If bred to an N/crd1 carrier, 50% of the offspring will be carriers and 50% will be affected.
– Carriers may be bred to normal animals (N/crd1 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/crd1 x N/crd1) is not recommended due to the possibility of 25% of the offspring being affected.
– Affected animals (crd1/crd1) should not be used for breeding.
Test Information: This mutation test identifies a three base pair deletion in exon 21 of the PDE6B gene.
Goldstein, O., Mezey, J.G., Schweitzer, P.A., Boyko, A.R., Gao, C., Bustamante, C.D., Jordan, J.A., Aguirre, G.D., Acland, G.M.: IQCB1 and PDE6B mutations cause similar early onset retinal degenerations in two closely related terrier dog breeds. Invest Ophthalmol Vis Sci 54:7005-19, 2013. Pubmed reference: 24045995. Doi: 10.1167/iovs.13-12915.
Further information is available at the Online Mendelian Inheritance in Animals website.