Washington
13 August 2009
 |
| A good night's sleep restores the emotional circuits of the brain |
Sleep is an essential process. Laboratory animals that are deprived of it for prolonged periods of time eventually die.
Nonetheless, Ying-Hui Fu with the University of California San Francisco says little is known about this basic human need.
"We do not know how our sleep is regulated," she said. "We do not know why some people need more sleep; why some people need less sleep; why most of us need eight hours of sleep; why, when we do not sleep, we do not function very well. We just do not know much about sleep at all."
Fu says sleep can be induced in humans when they drink alcoholic beverages or take sleeping pills. But she says no specific gene had been discovered that appeared to be involved in regulating sleep - until now.
Fu's research team stumbled across the sleep gene while looking for a molecular mechanism underlying circadian rhythms - a natural internal clock that regulates the shift between sleep and wakefulness during a 24-hour period.
In the course of their studies, Fu says researchers identified a genetic mutation in people who go to bed at a normal time but sleep only for about six hours, feeling as refreshed when they wake up as those who appear to need eight hours or more of sleep.
"We have these human subjects that carry this mutation and they look fine," she said.
Investigators genetically engineered mice to carry the mutation, and compared their sleep cycles and brain activity to rodents that did not have the genetic abnormality. They found that those with the gene slept less and were awake for longer periods of time. Mice with the mutation also were more energetic than normal mice, after being deprived of sleep.
Although the gene mutation is thought to be extremely rare, Fu says it is a significant find for sleep researchers.
"We essentially do not know anything about how sleep is regulated," she said. "But this gene is kind of opening a door for us to say, 'Now we have this gene and we know it affects human sleep quantity.'"
Fu adds that the gene might be related to other medical conditions.
"It is too early for me to make any conclusion because now that we have this mouse model, we can use a mouse to test whether mice that carry this mutation have metabolic problem[s] or they have psychiatric problem[s] or they have psychological problem[s]. We can start going into this field," she said.
Fu and her colleagues will also examine whether the gene controls the amount of sleep a person needs as well as the drive to fall asleep.
It is thought that sleep is also controlled by homeostasis, an internal process that keeps track of how much sleep people need and makes them feel tired so they will go to bed.
The study on the sleep gene is published this week in the journal Science.