Breeds Affected: Labrador Retriever
Samples Accepted: Blood, Buccal Swab
Disease Information: Dogs affected with canine narcolepsy (canarc-1) usually show symptoms before 6 months of age. They may be unusually sleepy during the day, drop suddenly from wakefulness into REM sleep, and can become cataleptic when startled.
Inheritance Information: Narcolepsy 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/nar The dog is a carrier, and can pass the allele on to approximately 50% of any offspring. If bred to another N/nar carrier, approximately 25% of the offspring will be normal, 50% will be carriers, and 25% will be affected.
nar/nar The dog is affected with narcolepsy. If bred to a normal animal, 100% of the offspring will be carriers. If bred to a N/nar carrier, 50% of the offspring will be carriers and 50% will be affected.
– Carriers may be bred to normal animals (N/nar 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/nar x N/nar) is not recommended due to the possibility of 25% of the offspring being affected.
– Affected animals (nar/nar) should not be used for breeding.
Test Information: This mutation test identifies a single base change that causes a deletion of exon 6 in the HCRTR2 gene. Animals which have two copies of this allele are affected, and animals with one copy are clinically-normal carriers.
Lin, L., Faraco, J., Li, R., Kadotani, H., Rogers, W., Lin, X.Y., Qiu, X.H., de, Jong, P.J., Nishino, S., Mignot, E.: The sleep disorder canine narcolepsy is caused by a mutation in the hypocretin (orexin) receptor 2 gene. Cell 98:365-376, 1999. Pubmed reference: 10458611
Further information is available at the Online Mendelian Inheritance in Animals website.