Mitochondrial Origin of Sleep Pressure: A Nature Study in Drosophila

Forum topic · ✨步子哥 · 2025-10-01

Summary

A 2025 Nature study by Sarnataro, Velasco, Monaco, Kempf, and Gero Miesenböck (University of Oxford group) reveals a physical, mitochondrial explanation for sleep pressure. Using single-cell RNA sequencing of sleep-control neurons (dFBNs) in fruit flies, the authors found that sleep deprivation selectively upregulates genes for mitochondrial respiration and ATP synthesis while downregulating synaptic genes. Sleep deprivation also fragments mitochondria (via Drp1 recruitment), increases mitochondria-ER contacts, and enhances mitophagy—all reversible with recovery sleep and blunted by electron overflow channels such as AOX. Manipulating mitochondrial fission or fusion bidirectionally alters both sleep and neuronal excitability: hyperfused mitochondria increase excitation and sleep, fragmented mitochondria decrease them. ATP levels in dFBNs rise after enforced wakefulness, and uncoupling electron flux from ATP synthesis relieves sleep pressure, whereas exacerbating the electron supply–ATP demand mismatch promotes sleep. The proposed mechanism centers on electron leakage from overloaded CoQ pools, sensed by the Hyperkinetic protein (Shaker potassium channel beta subunit) through lipid peroxidation-derived carbonyls. The authors argue sleep is an inevitable consequence of aerobic metabolism, sharing origins with hunger and aging.

Mitochondrial Origin of Sleep Pressure

Authors: Raffaele Sarnataro, Cecilia D. Velasco, Nicholas Monaco, Anissa Kempf & Gero Miesenböck Journal: *Nature*, Vol 645, 18 September 2025

Background

Sleep pressure is the process variable of sleep homeostasis, but it has lacked a physical explanation. Although prolonged wakefulness correlates with many brain changes—neuronal firing patterns, synaptic strength, subcellular organization, metabolite concentrations, metabolic and gene-expression programs—it has been unclear whether these are causes or consequences of sleep need. This study provides the first demonstration of a mitochondrial origin of sleep pressure, directly linking mitochondrial function to sleep regulation and suggesting new targets for sleep and metabolic disorders.

Methods

Single-cell RNA sequencing (10X Chromium): transcriptomes of single cells from rested and sleep-deprived Drosophila brains, focusing on dorsal fan-shaped body neurons (dFBNs) isolated by FACS of GFP-expressing cells; differential expression and GO enrichment analysis.
Mitochondrial morphology: optical photon reassignment microscopy (OPRM) and confocal laser scanning microscopy (CLSM); SPLICSshort sensors for mitochondria–ER contacts; mitoQC ratio sensors for mitophagy.
Electrophysiology: whole-cell patch-clamp recordings from dFBNs in vivo.
ATP measurement: genetically encoded sensors (iATPSnFR, ATeam) with two-photon imaging.
Behavior: Trikinetics activity monitoring; sleep deprivation by mechanical perturbation or thermogenetics.

Key Findings

After sleep deprivation, dFBNs selectively upregulate transcripts encoding electron transport chain complexes I–IV, ATP synthase (complex V), the ATP–ADP carrier sesB, and TCA cycle enzymes, while downregulating synaptic assembly, vesicle release, and presynaptic plasticity genes. This signature is specific to dFBNs and absent in antennal lobe projection neurons and Kenyon cells.
Sleep deprivation reduces mitochondrial size, elongation, and branching and increases mitochondrial number, indicating fission, with Drp1 relocalizing from cytosol to mitochondria. These changes reverse during recovery sleep and are attenuated by alternative oxidase (AOX) electron overflow.
Sleep deprivation increases mitochondria–ER contact sites and mitophagy.
Inducing or blocking fission/fusion in dFBNs bidirectionally alters sleep and neuronal electrical properties: hyperfused mitochondria increase excitability and sleep; fragmented mitochondria decrease both.
dFBN ATP concentrations rise after enforced wakefulness (reduced ATP consumption during wake-mediated inhibition). Uncoupling electron flux from ATP synthesis relieves sleep pressure; phot-driven proton pumping to boost ATP synthesis exacerbates the mismatch and promotes sleep.

Mechanism

The core mechanism is the balance between electron supply through the mitochondrial respiratory chain and ATP demand:

During waking, reduced neuronal activity means low ATP demand, high proton-motive force, high ATP/ADP ratio, and high NADH/NAD+—overfilling the CoQ pool and increasing electron leakage as superoxide/ROS.
Hyperkinetic (the beta subunit of the Shaker potassium channel, an unusual aldoketone reductase with tightly bound NADPH) lets dFBNs gauge electron leakage by counting the reduction of lipid peroxidation-derived carbonyls at its active site—acting as an early-warning system.
Mitochondrial fission (Drp1) lowers excitability and sleep; fusion (Opa1, Marf, with phosphatidic acid produced by mitoPLD and stabilized by Mitoguardin/Miga) raises both. Fission–fusion balance is part of a feedback loop correcting NADH-supply/ATP-demand mismatches.

The authors propose that sleep is an inevitable consequence of aerobic metabolism—the innovation that maximized free-energy yield from electron transport after the two great rises in atmospheric oxygen (2.4 billion and 750–570 million years ago), enabling the Cambrian explosion and the emergence of energy-hungry nervous systems. Sleep and hunger may share mitochondrial origins, with electrons flowing through their respective feedback controllers' respiratory chains like sand through an hourglass.

Conclusions

Sleep pressure originates from mismatch between mitochondrial electron supply and ATP demand, causing electron leakage and ROS.
Mitochondrial dynamics in sleep-control neurons directly govern sleep and neuronal excitability.
Sleep likely serves an ancient metabolic purpose, mechanistically related to aging and metabolic disease.

Future directions: verify conservation in mammals; test how mitochondrial dysfunction affects sleep; develop therapeutics targeting mitochondrial dynamics or the electron transport chain; explore shared mechanisms with metabolic disease and age-related mitochondrial decline.