Circadian photoreceptor CRYPTOCHROME promotes wakefulness under short winter-like days via a GABAergic circuitry.

Lack of the circadian photoreceptor cryptochrome (CRY) leads to increased sleep under short winter-like days in fruit flies, resembling winter hypersomnolence in SAD.

• Why it matters: Understanding how sleep is regulated during short days can shed light on the mechanisms behind winter sleepiness in seasonal affective disorder, which affects up to 10% of the population.
• What they did: Chen et al. studied fruit fly mutants of circadian clock genes under varying day lengths and found that CRY functions in GABA-synthesizing neurons to promote wakefulness during short days by downregulating GABAergic tone.
• The result: The findings suggest that CRY enhances wakefulness under short-day conditions and that similar mechanisms may be conserved in mammals, offering potential targets for modulating sleep in SAD and other conditions.