Breeds Affected: German Shepherd Dog
Samples Accepted: Blood, Buccal Swabs
Disease Information: Achromatopsia-2 (ACHM-2) is caused by a degeneration of cone cells just after the completion of retinal development, and is usually diagnosed between 8-12 weeks of age. Affected pups have day-blindness in bright light, but normal vision in dim light. The condition is not obvious on ophthalmoscopic examination, and vision does not deteriorate further with time.
Inheritance Information: Achromatopsia 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/achm2 The dog is a carrier, and can pass the allele on to approximately 50% of any offspring. If bred to another N/achm2 carrier, approximately 25% of the offspring will be normal, 50% will be carriers, and 25% will be affected.
achm2/achm2 The dog is affected. If bred to a normal animal, 100% of the offspring will be carriers. If bred to a N/achm2 carrier, 50% of the offspring will be carriers and 50% will be affected.
– Carriers may be bred to normal animals (N/achm2 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/achm2 x N/achm2) is not recommended due to the possibility of 25% of the offspring being affected.
– Affected animals (achm2/achm2) should not be used for breeding.
Test Information: This mutation test identifies a single base change in exon 7 of the CNGA3 gene.
Tanaka, N., Dutrow, E.V., Miyadera, K., Delemotte, L., MacDermaid, C.M., Reinstein, S.L., Crumley, W.R., Dixon, C.J., Casal, M.L., Klein, M.L., Aguirre, G.D., Tanaka, J.C., Guziewicz, K.E.: Canine CNGA3 Gene Mutations Provide Novel Insights into Human Achromatopsia-Associated Channelopathies and Treatment. PLoS One 10:e0138943, 2015. Pubmed reference: 26407004. DOI: 10.1371/journal.pone.0138943
Further information is available at the Online Mendelian Inheritance in Animals website.