Two mutations that influence the amount and type of sleep experienced by mice are reported online in Nature this week. The results are an important step towards understanding the mechanisms that govern slumber.
All animals sleep, yet despite its ubiquitous nature, surprisingly little is known about the cellular and molecular signals that underpin this most fundamental behaviour. Hiromasa Funato and colleagues identify two mutations that affect the sleep/wake balance. One, affecting the Sik3gene, causes a profound reduction in total time spent awake, owing to an increased inherent need for sleep. In this case, the amount of non-REM (rapid eye movement) sleep increases. A second mutation, in the Nalcn gene, reduces the total amount and episode length of REM sleep, apparently by making REM-sleep-inhibiting neurons more excitable.
The authors reached their results using a method called forward genetic screening. They looked at the sleep patterns of more than 8,000 mice with randomly generated genetic mutations, then looked for genetic changes in animals with unusual sleep patterns. They identified two pedigrees of mice that they dubbed Sleepy and Dreamless, which led to the discovery of the Sik3 and Nalcn mutations, respectively. The results highlight the potential of this approach to identify novel genes and pathways involved in sleep regulation.