Many of us are zombies without 8 hours of sleep, while envied others seem to get by just fine on much less. Now geneticists have homed in on the first gene in the general population that seems to influence how much sleep we need.
Sleep interests biologists in part because it varies with other factors, such as weight, that make people more prone to diabetes or heart disease. (The larger a person's body mass index, the less they generally sleep.) In search of sleep genes, a group of European researchers studied populations in seven countries, from Estonia to Italy, for a total of 4260 subjects. Each one filled out a simple questionnaire asking about his or her sleep habits and donated a DNA sample. The researchers then scanned the participants' DNA for thousands of genetic markers, looking for ones that were more common in people who slept more than those who slept less.
Sleep duration correlated strongly with a single genetic marker in a gene called ABCC9. When allowed to sleep as long as they want, those who have two copies of one version of this marker sleep on average 6% less than those carrying two copies of the other version, or about 7.5 hours versus 8 hours, says postdoc Karla Allebrandt, who is leading the study at the Centre for Chronobiology headed by Till Roenneberg at the University of Munich in Germany. Allebrandt presented the work last week at the annual meeting of the American Society of Human Genetics in Washington, D.C.
The ABCC9 gene codes for a protein called SUR2 that is part of a potassium channel, a structure that funnels potassium ions into and out of cells. When the researchers knocked down the corresponding gene in two species of fruit flies, the flies slept significantly less at night compared with controls, Allebrandt reported.
Although another gene, Dec2, has also been linked to sleep duration, so far it has been found only in certain families. ABCC9 is the first gene with such a strong association with sleep duration detected in the general population. Allebrandt says that because the SUR2 protein is also involved in heart disease and diabetes, the finding that it impacts sleep should also interest researchers working on those diseases.
Researchers have previously linked other potassium channel genes to sleep duration in flies, notes Paul Shaw, a neurobiologist at Washington University School of Medicine in St. Louis, Missouri. The fact that such a basic finding has now been backed up by a genetic study in people "makes the story that much more important," says Shaw, who wasn't at the meeting but has seen an abstract of the work. "It is very elegant that the same gene can influence the same behavior in both humans and flies."