Forward-genetics analysis of sleep in randomly mutagenized mice

Abstract

Summary Sleep is a behavior conserved from invertebrates to vertebrates, and tightly regulated in a homeostatic manner. The molecular and cellular mechanism determining the amount of rapid eye movement sleep (REMS) and non-REMS (NREMS) remains unknown. Here we identified two dominant mutations affecting sleep/wakefulness through an electroencephalogram/electromyogram-based screening of randomly mutagenized mice. A splicing mutation of the Sik3 protein kinase gene causes a profound decrease in total wake time, due to an increase in inherent sleep need. Sleep deprivation affects regulatory-site phosphorylation of the kinase. Sik3 orthologues regulate sleep also in fruit flies and roundworms. A missense mutation of the leak cation channel NALCN reduces the total amount and episode duration of REMS, apparently by increasing the excitability of REMS-inhibiting neurons. Our results substantiate the utility of forward genetic approach for sleep behaviors in mice, demonstrating the role of SIK3 and NALCN in regulating the amount of NREMS and REMS, respectively.

The adenosine-mediated, neuronal-glial, homeostatic sleep response

“…Although glial metabolic control of synaptic strength is of central importance it seems likely that other aspects of sleep related homeostasis may eventually be characterized. A recent forward genetic screen for sleep genes has implicated a gene encoding a protein kinase, Sik3 by showing a gain of function mutant, named “sleepy” (the mutation is a loss of one of the exons of Sik3 ) causes a constant state of sleep need in mice (35). This suggests that a sleep-need related gene network extending beyond the ADORA1-HOMER1a signaling pathway clearly warrants further examination.…”

To sleep or not to sleep: neuronal and ecological insights

“…Among the proposed substances and mechanisms involved in promoting sleep are the neuromodulator adenosine, and its receptors A1 and A2 A , as well as cytokines such as interleukin-1 and tumor necrosis factor-α, prostaglandin D 2 , and Nitric oxide (NO) [35–37]. A recent forward-genetics screen in mice revealed two sleep mutants, Sleepy and Dreamless [38 •• ] . Sleepy is a gain-of-function mutant of Sik3 serine-threonine protein kinase involved in the transduction of the mTOR pathway [38 •• ].…”

“…A recent forward-genetics screen in mice revealed two sleep mutants, Sleepy and Dreamless [38 •• ] . Sleepy is a gain-of-function mutant of Sik3 serine-threonine protein kinase involved in the transduction of the mTOR pathway [38 •• ]. Sleepy mutants show increased NREM sleep amount.…”

“…Sleepy mutants show increased NREM sleep amount. Dreamless mutants, that have a mutation in the sodium leak channel NALCN, show a decrease in REM sleep amount and episode duration [38 •• ]. Although the precise mechanisms by which these mutations modulate sleep need are still unclear, the use of an unbiased forward-genetics approach in mammals will likely lead to major insights into the pathways and mechanisms of sleep regulation.…”

Whole exome sequencing reveals a functional mutation in the GAIN domain of the Bai2 receptor underlying a forward mutagenesis hyperactivity QTL

“…We and others have had some success in combining forward mutagenesis, QTL mapping, and next generation sequencing to identify mutations in individual mouse genes that impact complex behavioral traits (Andrews et al 2012; Funato et al 2016; Gallego-Llamas et al 2015; Ha et al 2015; Hossain et al 2016; Kumar et al 2011; Militi et al 2016; Simon et al 2015), and while other approaches are also effective, there will likely be an important role for this screening approach in the future.…”