Kolesnik, A. | bioRxiv Science

bioRxiv2021

Polyamine elevation and nitrogen stress are toxic hallmarks of chronic sleep loss in Drosophila melanogaster

Chronic sleep loss profoundly impacts health in ways coupled to metabolism; however, much existing literature links sleep and metabolism only on acute timescales. To explore the impact of chronically reduced sleep, we conducted unbiased metabolomics on heads from three Drosophila short-sleeping mutants. Common features included elevated ornithine and polyamines; and lipid, acyl-carnitine, and TCA cycle changes suggesting mitochondrial dysfunction. Biochemical studies of overall, circulating, and excreted nitrogen in sleep mutants demonstrate a specific defect in eliminating nitrogen, suggesting that elevated polyamines may function as a nitrogen sink. Both supplementing polyamines and inhibiting their synthesis with RNAi regulated sleep in control flies. Finally, both polyamine-supplemented food and high-protein feeding were highly toxic to sleep mutants, suggesting their altered nitrogen metabolism is maladaptive. Together, our results suggest polyamine accumulation specifically, and nitrogen stress in general, as potential mechanisms linking chronic sleep loss to adverse health outcomes.

neuroscience↗

bioRxiv2020

Drosophila clock cells use multiple mechanisms to transmit time-of-day signals in the brain

Regulation of circadian behavior and physiology by the Drosophila brain clock requires communication from central clock neurons to downstream output regions, but the mechanism by which clock cells regulate downstream targets is not known. We show here that the pars intercerebralis (PI), previously identified as a target of the morning cells in the clock network, also receives input from evening cells. We determined that morning and evening clock neurons have time of day dependent connectivity to the PI, which is regulated by specific peptides as well as by fast neurotransmitters. Interestingly, PI cells that secrete the peptide DH44, and control rest:activity rhythms, are inhibited by clock inputs while insulin-producing cells are activated, indicating that the same clock cells can use different mechanisms to drive cycling in output neurons. Inputs of morning cells to the DILP2+ neurons are relevant for the circadian rhythm of feeding, reinforcing the role of the PI as a circadian relay that controls multiple behavioral outputs. Our findings provide mechanisms by which clock neurons signal to non-clock cells to drive rhythms of behavior. Significance StatementDespite our growing understanding of how the fly clock network maintains free-running rhythms of behavior and physiology, little is known about how information is communicated from the clock network to the rest of the brain to regulate behavior. We identify glutamate and acetylcholine as key neurotransmitters signaling from clock neurons to the pars interecerebralis (PI), a clock output region regulating circadian rhythms of sleep and metabolism. We report a novel link between Drosophila evening clock neurons and the PI, and find that the effect of clock neurons on output neuron physiology varies, suggesting that the same clock cells use multiple mechanisms simultaneously to drive cycling in output neurons.

neuroscience↗