Don’t need much sleep? Mutation linked to thriving with little rest

 A new study published in Proceedings of the National Academy of Sciences has identified a genetic mutation linked to people who naturally require very little sleep without suffering negative effects. These “naturally short sleepers” function well on just three to six hours of sleep per night, compared to the typical eight. Led by neuroscientist Ying-Hui Fu at the University of California, San Francisco, the research highlights a mutation in the gene SIK3, which may play a role in reducing sleep needs by supporting brain homeostasis—a process thought to help reset the brain during sleep.

Fu’s team first began studying short sleepers in the 2000s, identifying a mutation in the circadian rhythm gene of a mother and daughter. Since then, they’ve discovered five mutations across four genes associated with this trait. In the most recent study, they introduced the SIK3 mutation into mice, which then required about 31 minutes less sleep per day and showed heightened enzyme activity at brain synapses.

Although this mutation alone doesn’t cause drastic reductions in sleep need, it adds to a growing understanding of the genetic basis of sleep. Researchers hope these findings could eventually lead to treatments for sleep disorders or new insights into how sleep is regulated in the human brain.

Do Genes Control Your Sleep?

Recent studies suggest that sleeping too much or sleeping too little could be genetically linked. Abnormal sleeping patterns are connected to the regulation of thyroid hormone levels, specifically the DNA region located close to the PAX8 gene. Excessive sleepers are those who sleep more than 10 hours a day, and this condition is called hypothyroidism which occurs when the thyroid glands do not produce enough thyroid hormones. Hyperthyroidism is when too many thyroid hormones are produces which  results in insomnia, and those affected sleep less than 6 hours a day.

There is another sleeping pattern where people can function normally with only 4-6 hours of sleeping. This sleep pattern is a result of a mutation in the DEC2 gene, and typically expressed as falling asleep between 11pm and midnight, and waking up as early as 4 pm. This mutation results in alertness decreasing late at night allowing individuals to fall asleep faster, and waking you up alert and ready in the early morning. This mutation is rare, but different sleep patterns are controlled by different genes.

Mouse mutants with sleep defects may shed light on the mysteries of sleep

Despite how vital of a role sleep plays with our abilities to function on a daily basis, studies regarding sleep transition patterns are a road less traveled by for scientists. Researchers have hypothesized that there is a substance that grows and builds as our bodies are awake, and it recovers during restful sleep, but researchers are still unsure what is going on in our brains and why. To avoid getting skewed results or creating a biased trial, researchers induced random genetic mutations in 8,000 mice and used electroencephalograpy (EEG) to observe any abnormal sleeping patterns due to genetic perturbations. There were two mutations identified and labeled as Dreamless and Sleepy which were then mapped to determine the location in the genome.

Dreamless mice's mutation was pinpointed to the sodium channel and were observed to have less rapid eye movement (REM sleep) when compared to the Sleepy mice. Researchers noted that the mutation is responsible for Dreamless mice having reduced REM sleep, and it resulted from the mutation increasing the usage of the leaky sodium channel which was responsible for regulation neuronal excitability, these neuronal populations then stop REM sleep, leading to an increased excitability, explaining the abnormal sleep pattern.
Sleepy mice on the other hand, require more sleep (approximately 1/3 more than Dreamless mice), which was one of the questions the researchers were determined to answer. The mutation was carried on the Sik3 kinase gene which phosphorylates proteins and is likely involved in several signaling pathways. The first step taken was to observe the circadian rhythms of these mice, and surprisingly no disturbances were found. The next step was to attempt to arouse them with different types of environmental and pharmocological stimuli, whether it be a change in cages or introducing caffeine. But the Sleepy mice exhibited no change and scientists concluded that although they observed an increase in sleep, there were no obvious physiological reasons as to why and it still remains a mystery. Researchers hope that determining the kinase gene will aid in them diving deeper into this research to find some definitive solutions for human medicine.
This research that was conducted, was definitely a step in the correct direction. Although the results do not fully explain all of our questions regarding abnormal sleep patterns, the fact that the researchers were able to induce mutations and find the accurate location, unlocks one door to this maze of possibilities.

https://www.sciencedaily.com/releases/2016/11/161102144218.htm