Analysis of EGFR-dependent sleep in C. elegans

Disordered sleep impairs cognitive performance, and chronic sleep loss is associated with increased risk of cardiometabolic diseases including obesity and hypertension. Despite the fundamental importance of sleep, its function remains controversial and the molecular mechanisms by which it is executed are only beginning to be elucidated. Sleep is recognized to be regulated by conserved genetic mechanisms, and in the past decade the sleep field has expanded to non- mammalian organisms, allowing the application of novel genetic approaches. We have developed an inducible-sleep system in the nematode C. elegans, and we are using the powerful molecular- genetic tools of this system to discover novel components of sleep regulation. We have found that forced expression of the C. elegans Epidermal Growth Factor (EGF) homolog LIN-3 induces a sleep-like state at any stage. By assaying for resistance to this effect we have identified several effectors of EGF-induced sleep, including the EGF receptor (LET-23/EGFR) and the ERG (ether-a- go-go related gene) homolog UNC-103, a voltage-gated potassium channel. We aim to determine the neurons in which UNC-103 activity is required for the inhibition of activity during sleep. We will examine potential changes in UNC-103 levels and localization in response to EGF expression, to make a connection between sleep signals and their downstream effects on neuronal excitability. Our studies are expected to shed light on mammalian sleep regulation, as EGF ligand administration in mammals has a conserved soporific effect. We will also investigate the timing of C. elegans sleep behavior, which occurs rhythmically with molting rather than with circadian periodicity. We will examine LIN-3 expression for oscillation with the molting cycle, to connect behavior with developmental timing cues. This analysis is relevant to the regulation of sleep by biological clocks in mammals, as the molting cycle is regulated by the C. elegans homolog of the circadian gene PER. Lastly, we will identify additional effectors of sleep regulation. We have found that EGFR activation within a single neuron, ALA, triggers EGF-induced sleep. We hypothesize that this neuron releases a signal that in turn triggers sleep across the neuronal network. We will identify this signal through RNAi-based functional genomics, and characterize its function using molecular-genetic approaches.