- Neuroscientists found two genes that regulate mammals’ REM sleep.
- These two receptors are known as Chrm1 and Chrm3.
- Removing Chrm1 reduces and fragments REM sleep, while knockout of Chrm3 decreases the length of non-REM sleep.
Sleep is a universal reoccurring state of body and mind, characterized by changes in voluntary muscles, sensory activity, and consciousness. Until the early 1950s, people believed that sleep is a passive activity of our daily routines. We now know that the human brain remains very active during the sleep cycle.
Sleep affects our mental and physical health in several ways that we have just begun to understand. During sleep, humans physically restore themselves, removing metabolic wastes and consolidating memories. Most of the ‘restoration’ happens during deep sleep, during which heart rate, body temperature, and brain oxygen consumption reduces.
In higher vertebrates like birds and mammals, sleep is categorized in two stages: rapid eye movement (REM) sleep and non-REM sleep. REM is a mysterious phase of sleep in which our brain remains as active as it is during wakefulness, and this stage is known to play a crucial role in maintaining healthy physical and mental life. However, the neurobiology behind this phase is still not well-understood.
Recently, neuroscientists at the RIKEN Center for Biosystems Dynamics Research and the University of Tokyo discovered two genes that regulate our REM sleep. They demonstrated that duration of REM sleep drastically reduces to negligible levels in the absence of these two genes in a mouse model.
How It’s Different From Past Studies?
Previous studies have shown that acetylcholine (chemical emitted by nervous system neurons to activate muscles) and its receptor are responsible for regulating REM sleep. This chemical is copiously released in some portions of the brain during both wakefulness and REM sleep. But due to the complex neural network, researchers were not able to determine which receptors were controlling REM sleep.
In this study, scientists used advanced genetic tools to alter mouse genes and perform genetic screening for different parameters whose obstruction would lead to sleep abnormalities. They tested various genes that encode multiple acetylcholine receptors and knocked out all of them except the two.
Courtesy of researchers
These two receptors are known as Chrm1 and Chrm3. It turns out the loss of these two receptors highly affects the sleep cycle. They are widely spread in different parts of the brain. The experiment showed that removing Chrm1 reduces and fragments REM sleep, while knockout of Chrm3 decreases the length of non-REM sleep. The mice somehow survived but completely failed to experience REM sleep when they removed both genes.
In the future, researchers will investigate whether these two genes play any role in basic biological functions like memory and learning. Also, this research opens a new door to study underlying cellular and molecular functions, and ultimately define the phase of REM sleep, which hasn’t been clearly explained till date.