A genetic variant that predisposes to narcolepsy has been identified, according to a study published online this week in Nature Genetics. Narcolepsy is characterized by excessive daytime sleepiness and muscle weakness that may lead to collapse. It occurs in approximately 1 in 2,500 individuals in the United States and Europe, but is at least 4 times more frequent in Japanese.
Katsushi Tokunaga and colleagues carried out a genome-wide association of Japanese individuals, and found one variant to be significantly associated with risk of narcolepsy. They also found support for the association in Koreans, but not in individuals of European or African descent, probably because the frequency of the risk variant is much lower in the latter two populations.
The risk variant is located between the genes CPT1B and CHKB, each of which is a reasonable candidate to have a role in the disorder. The gene CPT1B encodes an enzyme involved in fatty acid oxidation, which has been implicated in sleep regulation. CHKB encodes an enzyme that catalyzes the production of one of the major components of cellular membranes, which is a precursor to a molecule that has been linked to the sleep-wake cycle.
Katsushi Tokunaga (University of Tokyo, Japan)
Abstract available online.
(C) Nature Genetics press release.
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