Best1 shapes the depth and stability of NREM sleep

Abstract Sleep architecture is orchestrated by neuronal circuits, yet the contribution of astrocytes—particularly to the depth and continuity of sleep—remains incompletely understood. Mammalian sleep is composed of rapid eye movement (REM) and non-REM (NREM) stages, with NREM further subdivided into light and deep phases. While neuronal and neurotransmitter-based mechanisms of sleep regulation have been extensively characterized, the role of astrocytic signaling in deep NREM sleep has received relatively little attention. Bestrophin-1 (Best1) is a calcium-activated anion channel highly enriched in astrocytes, known to mediate non-vesicular release of gliotransmitters such as glutamate, D-serine, and GABA, and to influence neuronal excitability. Here, we identify Best1 as a critical regulator of deep NREM sleep. Immunohistochemistry revealed robust Best1 expression in astrocytes across sleep-regulating brain regions. EEG/EMG polysomnography in Best1 knockout (Best1-KO) mice demonstrated a selective disruption of deep NREM sleep, despite preserved total sleep time and overall NREM duration. Best1-KO mice exhibited shorter deep NREM bouts, attenuated delta-band (0.5–4 Hz) EEG power, and altered vigilance-state transitions, with reduced entry into and maintenance of deep NREM. Sleep trajectories were biased toward Wake → light NREM → REM transitions, frequently bypassing deep sleep stages. Spectral decomposition further confirmed diminished delta oscillations during NREM episodes. These findings establish Best1 as a substage-specific molecular gatekeeper of deep NREM sleep. By uncovering a glial mechanism that shapes sleep sub-architecture, this work highlights astrocytic ion signaling as a promising therapeutic target for disorders marked by fragmented or insufficient deep sleep, including those associated with aging and neurodegenerative disease.