At least in flies according to an article by Rogulja and Young in the March 30 edition of Science. The researchers discovered that depletion of the gene Rca1 (regulator of cyclin A1) by RNA interference decreased the amount of time each day that flies spent sleeping. This gene suppression caused the flies to have more but shorter sleeping periods in a day. The protein this gene encodes, Rca1, regulates cyclin A, which regulates cell cycle progression. So Rogulja and Young also tested to see if knocking down expression of cyclin A also disrupted sleeping patterns and indeed it did. Again, the flies took a greater number of sleeping periods but each was shorter than normal. The researchers ran several other tests and found that reducing the expression of cyclin A caused a delay in the flies ability to fall asleep and also caused them to be more easily awakened. These results suggest that cyclin A is critical to maintaining sleep patterns. As further evidence the researchers point out that cyclin A is expressed in about 50 neurons in the brains of adult flies and most of those neurons are somehow connected to “circadian clock” neuron. This also points to a role as a gate keeper of the sleep-wake pattern.