Researchers Edited Mice Genes to Stop Them from Dreaming

We spend nearly half of our lives asleep, but many of the physiological aspects involved with regulating shut eye are still a mystery to researchers. Of particular interest to sleep scientists are the molecular mechanisms behind Rapid Eye Movement (REM) sleep, which is characterized by heightened neural activity and the onset of dreams.

In research published today in Cell Reports, a team of Japanese scientists identified two key genes involved with the regulation of REM sleep. Moreover, when these researchers used the gene editing technology CRISPR to “knockout” the genes in mice, they found that they reduced REM sleep “to an almost undetectable level.”

It has been known for decades that a neurotransmitter—a chemical that sends information between brain cells—called acetylcholine was critical to regulating REM sleep. Due to the abundance of acetylcholine released during both wakefulness and sleep and the complexity of the neural networks regulating sleep, however, it was unclear just which acetylcholine receptors were involved in regulating REM sleep.

To tackle this issue, the researchers used the gene editing tool CRISPR, which uses an enzyme called Cas9 to excise small portions of DNA and introduce genetic changes at that location. In this case, the researchers used CRISPR to selectively turn off the genes that encoded acetylcholine receptors.

When the researchers knocked out the genes encoding two acetylcholine receptors called Chrm1 and Chrm3, they found that this induced a “short sleep profile.” In other words, the brain activity of the mice showed that they were cycling through the stages of non-REM sleep, but showed almost no signs of descending into REM sleep.

Sleep research has identified REM sleep as a key component of our health in waking life. In particular, REM sleep has been linked to cognitive performance and has been shown to be important to the brain development of infants. As the researchers concluded their paper, the discovery of these REM-regulating genes will allow these links to be deeply tested in order to “verify whether REM sleep plays crucial roles in fundamental functions of the organism, such as learning and memory.”