Hypothesis

During NREM sleep, the glymphatic system actively transports extracellular neuronal DNA fragments and micronuclei to perivascular spaces where they are sampled by microglia. Detection of cytosolic DNA via the cGAS-STING pathway triggers a phagocytic program that eliminates genomically unstable neurons before clonal expansion. Sleep disruption impairs this flux, leading to accumulation of neuronal DNA, chronic cGAS-STING activation, microglial senescence, and failure to clear mutant neurons, thereby accelerating somatic CNV accumulation and neurodegeneration.

Mechanistic Rationale

• Glymphatic flux as a conveyor for nucleic acid debris – The 90% increase in CSF-interstitial fluid exchange during NREM sleep Glymphatic upregulation during NREM sleep is sufficient to mobilize not only soluble proteins but also larger macromolecular complexes such as extranuclear DNA fragments released from undergoing apoptosis or micronuclei rupture. Extracellular vesicles carrying DNA have been shown to travel along perivascular routes in other contexts Extracellular vesicle trafficking along perivascular spaces.
• Microglial DNA sensing via cGAS-STING – Microglia express cytosolic DNA sensors; cGAS activation yields STING-dependent type I interferon and phagocytic gene programs Microglial cGAS-STING signaling in neurodegeneration. In vitro, microglia phagocytose neurons bearing micronuclei only when STING is functional STING-dependent microglial phagocytosis of DNA‑positive neurons.
• Sleep loss shifts microglial phenotype – Chronic sleep deprivation elevates norepinephrine, contracts interstitial space, and blocks CSF flow Norepinephrine-mediated interstitial restriction during wakefulness. Concurrently, persistent cytosolic DNA triggers STING-driven microglial senescence or a maladaptive inflammatory state, reducing phagocytic capacity STING-mediated microglial senescence in aging brain.

Testable Predictions

1. Flux dependence – In mouse models with inducible neuronal CNVs (e.g., CRISPR‑Cas9‑mediated somatic deletion), pharmacological inhibition of glymphatic flow (via acetazolamide or AQP4 knockout) during NREM sleep will increase the retention of fluorescently labeled neuronal DNA fragments in the parenchyma and reduce microglial phagocytosis of these fragments (measured by pHrodo‑labeled debris colocalization with Iba1+ cells).
2. cGAS-STING requirement – Microglia‑specific deletion of cGAS or STING will abolish the sleep‑associated increase in phagocytosis of DNA‑positive neurons, even when glymphatic flow is intact.
3. Outcome on CNV burden – Chronic sleep fragmentation (4 h/night) in wild‑type mice will lead to a significant rise in somatic CNV load in cortical neurons after 3 months, quantified by single‑cell whole‑genome sequencing. This increase will be prevented by either (a) enhancing glymphatic flow via low‑frequency optogenetic stimulation of the locus coeruleus during sleep, or (b) pharmacological STING inhibition.
4. Human biomarker correlation – In older adults, CSF concentrations of neuronal DNA fragments (detected by digital PCR for neuron‑specific loci) will be inversely correlated with slow‑wave EEG power and directly correlated with plasma markers of microglial senescence (e.g., sCD163). Sleep‑intervention trials that increase slow‑wave sleep should reduce CSF neuronal DNA and improve microglial activation profiles.

Falsifiability

If blocking glymphatic transport fails to alter microglial uptake of neuronal DNA fragments or does not change somatic CNV accumulation despite confirmed sleep disruption, the hypothesis is falsified. Likewise, if enhancing glymphatic flow or inhibiting STING does not rescue the CNV burden under sleep‑deprived conditions, the proposed mechanistic link between sleep‑dependent glymphatic clearance and genomic surveillance is invalid.