Fruit flies do not sleep all night like humans, but they do manage to spend about half of their day in bouts of inactivity that have similarity to sleep in other species. Rogulja and Young searched for genes in neurons whose products regulated sleep. Depletion of the protein regulator of cyclin A1 (Rca1) caused the flies to be slow to go to sleep and to get less total sleep in a day because their sleep episodes were shorter. The mechanism by which Rca1 influences sleep is not yet clear. It appears not to disrupt circadian rhythms. However, the neurons that express Rca1 in the fly brain are located near the neurons that make up the circadian clock, potentially allowing for coordination of circadian behavior with sleep regulation.