Breeds Affected: Coton de Tuléar
Samples Accepted: Blood, Buccal Swabs
Disease Information: Canine Multifocal Retinopathy 2 (cmr2) is usually first noticed when pups are 10-14 weeks of age. Small light-coloured lesions develop, where the retina is separating/folding. In mild cases, there is little disruption of sight; in severe cases the condition may progress to blindness.
Inheritance Information: Cmr2 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/cmr2 The dog is a carrier, and can pass the allele on to approximately 50% of any offspring. If bred to another N/cmr2 carrier, approximately 25% of the offspring will be normal, 50% will be carriers, and 25% will be affected.
cmr2/cmr2 The dog is affected. If bred to a normal animal, 100% of the offspring will be carriers. If bred to a N/cmr2 carrier, 50% of the offspring will be carriers and 50% will be affected.
– Carriers may be bred to normal animals (N/cmr2 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/cmr2 x N/cmr2) is not recommended due to the possibility of 25% of the offspring being affected.
– Affected animals (cmr2/cmr2) should not be used for breeding.
Test Information: This mutation test identifies a change in the BEST1 gene (also known as VMD2).
Guziewicz, KE., Zangerl, B., Lindauer, SJ., Mullins, RF., Sandmeyer, LS., Grahn, BH., Stone, EM., Acland, GM., Aguirre, GD.: Bestrophin gene mutations cause canine multifocal retinopathy: a novel animal model for best disease. Invest Ophthalmol Vis Sci 48:1959-67, 2007. Pubmed reference: 17460247. DOI: 10.1167/iovs.06-1374.
Further information is available at the Online Mendelian Inheritance in Animals website.