Sleep neuron depolarization promotes protective gene expression changes and FOXO activation.

Sleep is an essential state that allows for recuperation and survival processes. Disturbing sleep triggers stress responses that promote protective gene expression. Sleep and its deprivation grossly impact gene expression, but little is known about how normal or disturbed sleep control gene expression. Central to the induction of sleep are sleep-active neurons, which inhibit wakefulness and promote survival. Sleep and sleep-active neurons are highly conserved. In Caenorhabditis elegans, the sleep-active RIS neuron is crucial for sleep and survival. Here, we show that RIS depolarization promotes the protective gene expression response that occurs during developmental arrest. This response includes the activation of FOXO/DAF-16 and expression of DAF-16 target genes such as HSP-12.6, a small heat-shock protein that is required for starvation survival. Disturbing sleep by mechanical stimulation increases RIS depolarization. RIS activation in turn activates DAF-16 and other genes required for survival. Hence, during normal sleep, RIS depolarization promotes protective gene expression. When sleep is disturbed, protective gene expression gets further increased by raised RIS depolarization. We thus link sleep-active neuron depolarization to protective gene expression changes and suggest that the cellular stress response following sleep deprivation could be understood as a safeguarding process that is caused by the overactivation of sleep-active neurons.