Control of sleep by cyclin A and its regulator.

How and why the brain reversibly switches from a waking to a sleep state remain among the most intriguing questions in biology. We show that cyclin A (CycA) and regulator of cyclin A1, essential cell cycle factors, function in postmitotic neurons to promote sleep in Drosophila melanogaster. Reducing the abundance of CycA in neurons delayed the wake-sleep transition, caused multiple arousals from sleep, and reduced the homeostatic response to sleep deprivation. CycA is expressed in ~40 to 50 neurons in the adult brain, most of which are intermingled with circadian clock neurons, suggesting functional interactions among neurons controlling sleep and circadian behavior.