Some rare individuals can get by with less sleep than the rest of us; after four to six hours, they are well-rested. Scientists have found that it’s because of their genes. Two of those genes have been identified by previous research, and now another has been revealed. This discovery has also shown that this gene stops the memory problems that are caused by sleep deprivation. Reporting in Science Translational Medicine, the researchers have suggested that this work can improve therapeutics that treat sleep disorders and improve the quality of sleep.
"Ten years ago, when we identified the first short sleep gene, the field of sleep genetics was in its infancy. People didn't think that genes could significantly influence sleep behaviors, and big breakthroughs were rare. Today the field is advancing much more rapidly, and we're beginning to get a better picture of how important your genes are to getting a good night's sleep," said the researcher that led the studies that revealed the three genes Ying-Hui Fu, Ph.D., a professor of neurology and member of the UCSF Weill Institute for Neurosciences. She discusses her research in the video below.
In this study, the scientists examined the genes of a father and son who average a short 5.5 and 4.3 hours of sleep per night. Most people need around eight hours or they will feel the effects of sleep deprivation. This father and his son don’t show any sign of the physical or mental problems that come with sleep deprivation.
"There are serious health consequences associated with sleep deprivation," noted the study co-author Louis Ptáček, M.D., a professor of neurology and a member of the Weill Institute. "People who are chronically sleep-deprived are more likely to suffer from obesity, diabetes, cardiovascular problems, depression and cognitive deficits."
Gene sequencing was done on samples from the father and son, and the researchers focused on a change in one letter or base pair of a gene called NPSR1. The gene codes for a protein on the surface of neurons, which is involved in the regulation of sleep. It plays a role in a wakefulness-promoting signaling pathway. The genetic mutation carried by the father and son is extremely rare, and is thought to occur in only one of every four million people.
The investigators modeled the mutation in mice, and found that when they carried the mutation, they slept less and were more active compared to normal mice. NPSR1 can activate proteins downstream of it in a biochemical pathway. The scientists also used a drug to trigger the activity of NPSR1 in normal and genetically modified mice, and found that in the modified mice, many more downstream proteins were activated; it was easier to trigger the mutant version of NPSR1 compared to the normal protein. Not only is the mutated NPSR1 easier to activate, it can switch other pathway components more efficiently.
After subjecting the mice to sleep deprivation and subsequent memory tests, the researchers observed memory problems in normal mice. The genetically modified mice carrying a mutant version of NPSR1 did not show those memory deficits, however.
"NPSR1 not only promotes short sleep, it also prevents memory problems that usually result from sleep deprivation," Fu explained. "This is the first gene that anyone's discovered that exerts a protective effect against one of the many adverse consequences of sleep deprivation."
"Not only does this discovery provides us with a better understanding of how genes contribute to an unusual sleep phenotype, it also offers up an appealing target for future therapies that may help treat sleep disorders or prevent certain cognitive deficits associated with lack of sleep," Ptáček concluded.
Sources: AAAS/Eurekalert! via University of California San Francisco, Science Translational Medicine