Breeds Affected: Briard
Samples Accepted: Blood, Buccal Swabs
Disease Information: CSNB is an early -onset eye disorder, which starts with affected animals having difficulty seeing in low lighting, and may progress into difficulties seeing in normal daylight.
Inheritance Information: CSNB 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/csnb The dog is a carrier, and can pass the allele on to approximately 50% of any offspring. If bred to another N/csnb carrier, approximately 25% of the offspring will be normal, 50% will be carriers, and 25% will be affected.
csnb/csnb The dog is affected. If bred to a normal animal, 100% of the offspring will be carriers. If bred to a N/csnb carrier, 50% of the offspring will be carriers and 50% will be affected.
– Carriers may be bred to normal animals (N/csnb 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/csnb x N/csnb) is not recommended due to the possibility of 25% of the offspring being affected.
– Affected animals (csnb/csnb) should not be used for breeding.
Test Information: This mutation test identifies a deletion in the RPE65 gene.
Veske, A., Nilsson, S.E.G., Narfstrom, K., Gal, A.: Retinal dystrophy of Swedish briard briard-beagle dogs is due to a 4-bp deletion in RPE65 Genomics 57:57-61, 1999. Pubmed reference: 10191083. DOI: 10.1006/geno.1999.5754
Aguirre, G.D., Baldwin, V., Pearce-Kelling, S., Narfström, K., Ray, K., Acland, G.M.: Congenital stationary night blindness in the dog: common mutation in the RPE65 gene indicates founder effect. Mol Vis 4:23, 1998. Pubmed reference: 9808841
Further information is available at the Online Mendelian Inheritance in Animals website.