An assault of the immune system on sleep centers of the brain may cause narcolepsy, according to a study published online in Nature Genetics.

Narcolepsy is an elusive autoimmune disorder linked to depletion of cells deep in the regulatory regions of the brain and characterized by sudden onset of daytime sleepiness. Scientists have now detected a significant association between narcolepsy and a gene variant found in individuals of European as well as of Asian ancestry. The gene encodes an important receptor used by T-cells of the immune system to recognize foreign proteins in the body.

Emmanuel Mignot and colleagues carried out a genome wide association study to identify novel areas of the genome associated with susceptibility for narcolepsy. They found three distinct DNA variants in the T-cell receptor gene that were associated with an increased risk of the disorder. Their finding is intriguing since the only previous genetic association with narcolepsy among Europeans, Asians, and African Americans has been with another gene variant that encodes a molecule expressed on white blood cells, called human leukocyte antigen, that is responsible for presenting 'foreign' proteins to T-cell receptors.

The variants identified by Mignot and colleagues represent a significant advance into unraveling the cause of the autoimmune component of this disorder. This is also the first involvement of T-cell gene variants to be documented for any disease.