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Mutated Gene Helps Some Survive on Less Sleep
August 14, 2009
Scientists at Univ. of California, San Francisco have discovered the first gene involved in regulating the optimal length of human sleep.
The team identified a mutated gene that allows two members of an extended family to thrive on six hours of sleep a day rather than the eight to eight-and-a-half hours that studies have shown humans need over time to maintain optimal health. Working from this discovery, the scientists genetically engineered mice and fruit flies to express the mutated gene and study its impact.
While most Americans obtain less than eight hours of sleep a night (the average on non-work days is 7.4 hours), and some may feel they succeed with less when engaged in exhilarating work, domestic life or recreation, scientific evidence indicates the body suffers from this regimen over time.
Prof. Ying-Hui Fu says the study offers an opportunity to unravel the regulatory mechanism of sleep. Understanding these mechanisms could lead to interventions to alleviate pathologies associated with sleep disturbance.
Sleep remains a relatively inscrutable biological phenomenon. Scientists know that it is regulated in large part by two processes: circadian rhythms—genetic, biochemical and physiological mechanisms that wax and wane during a 24 hour period to regulate the timing of sleep, and homeostasis – unknown mechanisms that ensure that the body acquires over time the necessary amount of sleep, nudging it toward sleep when it has been deprived, prompting it out of sleep when it has received enough.
This regulation of sleep intensity is measured in non rapid eye movement sleep and REM sleep. Interactions between the circadian rhythms and homeostatic mechanisms influence the timing, duration and quality of sleep and wakefulness. But the details of the process are unknown.
In the current study, the team identified a small extended family in which a mother and her adult daughter had life-long shorter daily sleep requirements than most individuals. Fu’s lab then studied blood samples from these women and their extended family. They identified a mutation in a gene known as hDEC2, which is a transcription factor that represses expression of other genes and is implicated in the regulation of circadian rhythms.
Next, the team genetically engineered mice and fruit flies to express the mutated human gene, and postdoctoral fellow Ying He studied its impact on their behavior and sleep patterns.
Mice slept less, as seen in the extent of their scampering about in the dark over the course of 24 hours and in electroencephalography (EEG) and electromyography (EMG) measurements indicating reduced nonREM and REM sleep. He studied the creatures’ activity and sleep patterns by tracking the frequency of their movements through infrared light.
Next, the team compared the response of the genetically engineered mice and normal mice to the consequence of six hours of sleep deprivation. The engineered mice needed to compensate for their lost sleep to a much lesser extent – as seen in nonREM and REM measures – than their normal counterparts.
“These changes in sleep homeostasis in the mutant mice could provide an explanation for why human subjects with the mutation are able to live unaffected by shorter amounts of sleep throughout their lives,” says Fu.
The next step, she says, is determining the DEC2’s precise role. “We know the gene encodes a protein that is a transcriptional repressor and we know it makes the repressor’s activity weaker. But we don’t know if the weaker repressor is directly related to the shorter amount of sleep, because proteins can have many functions.”
Source: UCSF
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