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Circadian programming of the ellipsoid body sleep homeostat in Drosophila.

ABSTRACT: Homeostatic and circadian processes collaborate to appropriately time and consolidate sleep and wake. To understand how these processes are integrated, we scheduled brief sleep deprivation at different times of day in Drosophila and find elevated morning rebound compared to evening. These effects depend on discrete morning and evening clock neurons, independent of their roles in circadian locomotor activity. In the R5 ellipsoid body sleep homeostat, we identified elevated morning expression of activity dependent and presynaptic gene expression as well as the presynaptic protein BRUCHPILOT consistent with regulation by clock circuits. These neurons also display elevated calcium levels in response to sleep loss in the morning, but not the evening consistent with the observed time-dependent sleep rebound. These studies reveal the circuit and molecular mechanisms by which discrete circadian clock neurons program a homeostatic sleep center.

SUBMITTER: Andreani T

PROVIDER: S-EPMC9270026 | biostudies-literature | 2022 Jun

REPOSITORIES: biostudies-literature

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Publications

Circadian programming of the ellipsoid body sleep homeostat in <i>Drosophila</i>.

Andreani Tomas T Rosensweig Clark C Sisobhan Shiju S Ogunlana Emmanuel E Kath William W Allada Ravi R

eLife 20220623

Homeostatic and circadian processes collaborate to appropriately time and consolidate sleep and wake. To understand how these processes are integrated, we scheduled brief sleep deprivation at different times of day in <i>Drosophila</i> and find elevated morning rebound compared to evening. These effects depend on discrete morning and evening clock neurons, independent of their roles in circadian locomotor activity. In the R5 ellipsoid body sleep homeostat, we identified elevated morning expressi ...[more]

PMID: 35735904

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Project description:The ellipsoid body (EB) is a major structure of the central complex of the Drosophila melanogaster brain. Twenty-two subtypes of EB ring neurons have been identified based on anatomic and morphologic characteristics by light-level microscopy and EM connectomics. A few studies have associated ring neurons with the regulation of sleep homeostasis and structure. However, cell type-specific and population interactions in the regulation of sleep remain unclear. Using an unbiased thermogenetic screen of EB drivers using female flies, we found the following: (1) multiple ring neurons are involved in the modulation of amount of sleep and structure in a synergistic manner; (2) analysis of data for ΔP(doze)/ΔP(wake) using a mixed Gaussian model detected 5 clusters of GAL4 drivers which had similar effects on sleep pressure and/or depth: lines driving arousal contained R4m neurons, whereas lines that increased sleep pressure had R3m cells; (3) a GLM analysis correlating ring cell subtype and activity-dependent changes in sleep parameters across all lines identified several cell types significantly associated with specific sleep effects: R3p was daytime sleep-promoting, and R4m was nighttime wake-promoting; and (4) R3d cells present in 5HT7-GAL4 and in GAL4 lines, which exclusively affect sleep structure, were found to contribute to fragmentation of sleep during both day and night. Thus, multiple subtypes of ring neurons distinctively control sleep amount and/or structure. The unique highly interconnected structure of the EB suggests a local-network model worth future investigation; understanding EB subtype interactions may provide insight how sleep circuits in general are structured.SIGNIFICANCE STATEMENT How multiple brain regions, with many cell types, can coherently regulate sleep remains unclear, but identification of cell type-specific roles can generate opportunities for understanding the principles of integration and cooperation. The ellipsoid body (EB) of the fly brain exhibits a high level of connectivity and functional heterogeneity yet is able to tune multiple behaviors in real-time, including sleep. Leveraging the powerful genetic tools available in Drosophila and recent progress in the characterization of the morphology and connectivity of EB ring neurons, we identify several EB subtypes specifically associated with distinct aspects of sleep. Our findings will aid in revealing the rules of coding and integration in the brain.

Project description:Purpose: After identifying a difference in the response to sleep deprivation between the morning and evening, we assayed gene expression in a key homeostatic circuit in the Drosophila brain: the R5 ellipsoid body neurons. We sought to identify changes in gene expression in this circuit that are critical for the behavioral output. Methods: Flies expressing GFP via a restrictive R5 driver were entrained to a 12:12 light:dark paradigm at 25C. Mated females were then loaded into individual tubes with sucrose food and placed into behavior boards from Trinkinetics. Control flies were not subjected to any sleep deprivation and were collected in either the morning or evening. Experimental flies were subjected to 2.5 hrs of mechanical sleep deprivation (SD) via vortexing just before either the morning or evening. Following SD (or at the appropriate control timepoint), 40-50 brains were dissected out in dissecting saline with TTX, AP5, and DNQX to inhibit sodium channels, NMDA receptors, and AMPA receptors respectively. The brains were transferred to SM Active medium with channel blockers after dissection, then washed with dissecting saline before being digested with papain. Digestion was stopped after 30 minutes by the addition of SM Active medium with channel blockers. The brains were then triturated by manual pipetting to produce a single cell suspension. GFP+ cells were immediately sorted by fluorescence activated cell sorting into a single tube. 350-500 cells were collected per experiment. In total, we collected 12 samples, three replicates for each timepoint and condition. Cells were lysed in extraction buffer from the Arcturus PicoPure kit and stored at -80C until ready to process. RNA was extracted from each set of cells using the PicoPure kit, and then reverse transcribed into cDNA using a T7/polydT primer. One round of in vitro transcription using the MEGAScript kit was performed to amplify the RNA. Following IVT, library prep was performed using the TruSeq Stranded mRNA Library Prep Kit. We generated 30 million reads per sample on a NovaSeq. Analysis was performed using kallisto and sleuth.

Dataset Information

Circadian programming of the ellipsoid body sleep homeostat in Drosophila.

Publications

Circadian programming of the ellipsoid body sleep homeostat in <i>Drosophila</i>.

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