Circadian genes and the sleep-wake cycle

The regulation of virtually all behavioral, physiological, and molecular processes is influenced by whether an organism is asleep or awake. One of the defining characteristics of sleep and wakefulness is that these states are under strong circadian regulation. Rapid advances have been made in discovering and characterizing the genes that make up the molecular circadian clock. These genes are important in directing the timing of sleep and wakefulness, arguably the master output rhythm of the circadian clock. Surprisingly, clock genes have been found to exert more wide-ranging effects on sleep regulation and serve a role in modulating sleep-wake amount, sleep architecture, and the homeostatic response to sleep deprivation. Circadian clock genes have emerged as important genetic components in multiple aspects of sleep and wake regulation.