A gene variant has been discovered that allows carriers to function normally on less sleep than other people.
Researchers at the University of California, San Francisco (UCSF) found the rare mutation after examining the genomes of a family of natural short-sleepers: people who naturally only sleep 4-6 hours per night, and feel adequately rested.
'It's remarkable that we know so little about sleep, given that the average person spends a third of their lives doing it,' said joint senior author Louis PtáÄek, professor of neurology at the Weill Institute for Neurosciences at UCSF. 'This research is an exciting new frontier that allows us to dissect the complexity of circuits in the brain and the different types of neurons that contribute to sleep and wakefulness.'
The other senior author, Ying-Hui Fu, also a professor of neurology at the Weill Institute, was part of the team that discovered the first gene associated with short-sleeping (see BioNews 522). That gene was called DEC2, which was found to influence levels of orexin, a hormone that which regulates wakefulness – too little can cause narcolepsy.
The newly discovered variant is in a gene called ADRB1 which codes for a noradrenaline receptor. Noradrenaline acts as a hormone and neurotransmitter.
'We found that this gene codes for ß1-adrenergic receptor, and that the mutant version of the protein is much less stable, altering the receptor's function. This suggested it was likely to have functional consequences in the brain,' said Professor Fu.
Following the discovery, the researchers looked at cells expressing ADRB1 in the brain stems of mice. The brain stem is the part of the nervous system known to be associated with sleep regulation.
They found that in the normal mouse brain stems, cells with the ADRB1 receptor were active when mice were awake or in REM sleep, and quiet when in deep sleep. Stimulating these neurons in any sleep phase would cause the mice to wake immediately.
Cells in brain stems of mice with the ADRB1 mutation were more active than in the normal mice. The mice with the mutation slept on average nearly an hour per day less than normal mice. Humans with the mutation average two hours less sleep than their peers.
The researchers hope that understanding sleep better can have many therapeutic benefits.
'Sleep is one of the most important things we do,' said Professor Fu. 'Not getting enough sleep is linked to an increase in the incidence of many conditions, including cancer, autoimmune disorders, cardiovascular disease, and Alzheimer's.'
The work was published in the journal Neuron.