Jingjing Yan*¹, Sydney Christensen*^1,2, Kelsey Mainard*¹, Fumihiro Ito¹, Phil Zhang¹, Yangyuan Li¹, Wanhe Li^1,2

Histone monoaminylations represent a novel class of histone post-translational modifications (PTMs), in which monoamine neurotransmitters—such as dopamine, serotonin, and histamine—are covalently attached to the tail region of histone H3 via transamidation reactions. In Drosophila, monoaminergic neurotransmission and neural circuits play key roles in regulating sleep and wakefulness. We therefore hypothesized that this novel form of histone modification might play a direct role in controlling sleep in Drosophila.

Using a set of Drosophila neurogenetics tools, we found that perturbing histone monoaminylation caused nighttime sleep loss, specifically within a defined circadian window, indicating a defect in sleep maintenance. We conducted a large-scale, unbiased, circuit-based screen and identified the cell types that supported this histone monoaminylation-dependent sleep phenotype. Unexpectedly, we discovered that the inhibitory neurotransmitter γ-aminobutyric acid (GABA), which also contains a primary amine group, could similarly modify histone H3 via a transamidation reaction. This novel histone mark, termed histone H3-carboxypropylaminylation, along with other histone monoaminylation marks, exhibited circadian features and regulated sleep/wake behavior in a time-of-day-dependent manner. We employed a comprehensive set of biochemistry, genetic, and genomic approaches to further characterize the gene regulatory network underlying histone monoaminylation-dependent sleep regulation. Because monoamine biochemistry and histone proteins are remarkably conserved between humans and flies, this work may reveal epigenetic mechanisms of sleep regulation that are evolutionarily conserved.

*authors contributed equally.

1.Center for Biological Clocks Research, Department of Biology, Texas A&M University, College Station, TX 77843

2.Interdisciplinary Graduate Program in Genetics and Genomics, Texas A&M University, College Station, TX 77843

Funding Support: This work was supported by the Cancer Prevention and Research Institute of Texas (RR220021 to W.L.) and the National Institute of General Medical Sciences (GM150832 to W.L.).