Mutation linked to thriving with little rest
Baku, May 7, AZERTAC
Most people need around eight hours of sleep each night to function, but a rare genetic condition allows some to thrive on as little as three hours, according to Nature.
In a study published today in the Proceedings of the National Academy of Sciences1, scientists identified a genetic mutation that probably contributes to some people’s limited sleep needs.
Understanding genetic changes in naturally short sleepers — people who sleep for three to six hours every night without negative effects — could help to develop treatments for sleep disorders, says co-author Ying-Hui Fu, a neuroscientist and geneticist at the University of California, San Francisco.
“Our bodies continue to work when we go to bed”, detoxifying themselves and repairing damage, she says. “These people, all these functions our bodies are doing while we are sleeping, they can just perform at a higher level than we can.”
In the 2000s, Fu and her colleagues were approached by people who slept six hours or less each night. After analysing the genomes of a mother and daughter, the team identified a rare mutation in a gene that helps to regulate humans’ circadian rhythm, the internal clock responsible for our sleep–wake cycle. The researchers suggested that this variation contributed to the duo’s short sleep needs. That discovery prompted others with similar sleeping habits to contact the laboratory for DNA testing.
The team now knows several hundred naturally short sleepers. Fu and her colleagues have so far identified five mutations in four genes that can contribute to the trait — although different families tend to have different mutations.
The researchers engineered mice to have the same mutation in the DEC2 gene seen in human short sleepers. They discovered that DEC2 helps control levels of orexin, a hormone involved in maintaining wakefulness. (The sleep disorder narcolepsy is caused by too little of this hormone.) The mutation in DEC2 seems to work by partially releasing the breaks on orexin production.
DEC2 helps regulate circadian rhythms, the natural biological clock that dictates when hormones are released and influences behaviors such as eating and sleeping. DEC2 oscillates on a circadian schedule: rising during the day, but falling at night.
The new study suggests that DEC2 may lower your level of alertness in the evening by binding to and inhibiting MyoD1, a gene that turns on orexin production. Before dawn, DEC2 fades away, allowing MyoD1 to stimulate orexin production to wake you up and keep you alert throughout the day.
Fu says the mutation seen in human short sleepers weakens DEC2’s ability to put the breaks on MyoD1, leading to more orexin production and causing the short sleepers to stay awake longer. “The role of DEC2 is likely to make sure orexin is expressed in the right amount at the right time of day. It’s the time-keeper to make sure orexin levels match the circadian rhythm,” she explains.
The DEC2 mutation is very rare, but there are other gene mutations that act on different pathways to cause natural short sleep. Fu is studying these genes with the goal of better understanding sleep and its impact on our health.
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