Figure 6.

Model for sleep regulation of DVB neurite outgrowth and behavior

(A) We propose that DVB morphology in day 1 male C. elegans is determined by the balance of neurite extension and retraction (or pruning) after the L4 transition to adult. DVB neurite outgrowth leads to inhibition from DVB, which determines the time to spicule protraction. C. elegans with undisturbed sleep have a balance in extension and retraction of neurites. The movement quiescence during lethargus may result in conservation of energy.

(B) We suggest that DVB undergoes neurite extension without retraction in male C. elegans that experience sleep loss, with pruning being dependent on sleep, thus resulting in an imbalance between extension and retraction and an overall increase in DVB neurite outgrowth. The increase in DVB neurites results in an increase in DVB inhibition and a longer time to spicule protraction. While these males do not experience quiescence, therefore increasing energy expenditure, the increase in inhibition on spicule neurons and muscles, observed as slower spicule protraction, may conserve energy.

(C) In day 1 animals lacking sleep with mutations in nrx-1 or nlg-1, we hypothesize that sleep deprivation induced DVB neurite extension is not stabilized, leading to rebalance in extension and retraction, as both processes are affected (retraction impacted by lack of sleep). Therefore, DVB morphology is similar to controls and the time to spicule protraction is not increased. Lack of energy conservation due to impaired sleep and potential energy expenditure in spicule protraction neurons and muscles may lead to further loss of energy, and altered response to sleep deprivation may be detrimental.