https://www.scientificamerican.com/article/scientists-identify-genes-linked-to-rem-sleep/

Scientists have known about the stage of sleep called rapid eye movement, or REM—which is associated with dreaming as well as improved learning and memory—since the 1950s. Many of its mechanisms remain mysterious, however. Now a study has identified two genes that play a key role in REM.

Mice that lack the genes Chrm1 and Chrm3 sleep fewer hours than typical mice and have almost undetectable REM levels, the researchers find. This is the first time scientists have homed in on genes essential for REM sleep, says Hiroki Ueda of Japan's RIKEN Center for Biosystems Dynamics Research, who conducted the study published in August in Cell Reports.