Abstract
Sleep is a nearly universal feature of animal behaviour, yet many of the molecular, genetic, and neuronal substrates that orchestrate sleep/wake transitions lie undiscovered. Employing a viral insertion sleep screen in larval zebrafish, we identified a novel mutant, dreammist (dmist), with altered sleep-wake dynamics. CRISPR/Cas9-mediated disruption of dmist also led to behavioural hyperactivity and reduced sleep at night. The neuronally expressed dmist gene is conserved across vertebrates and encodes a small single-pass transmembrane protein that is structurally similar to the Na+,K+-ATPase regulator, FXYD1/Phospholemman. Disruption of either fxyd1 or atp1a3a, a Na+,K+-ATPase alpha-3 subunit associated with several heritable movement disorders in humans, led to decreased night-time sleep. As intracellular Na+ concentration is disrupted in dmist mutant brains after high neuronal activity similarly to atp1a3a mutants, but is also elevated specifically at night, we propose that sleep-wake stability is modulated by Dmist-dependent changes to Na+ pump function during sleep homeostatic challenge and at specific times of the day-night cycle.
Significance statement Sleep is an essential component of behaviour, but the genes that regulate sleep and wake states are still being uncovered. A viral insertion screen in zebrafish identified a novel sleep mutant called dreammist, in which a small, highly-conserved transmembrane protein is disrupted. The discovery of dreammist highlights the importance of a class of small transmembrane-protein modulators of the sodium pump in setting appropriate sleep duration.
Competing Interest Statement
The authors have declared no competing interest.