Genomic/Genetic Approaches to Sleep and Its Disorders.
Sleep occupies about one-third of our life. Although we spend much of our life doing this, we do not yet understand the function(s) of sleep. Recent data from expression profiling studies comparing gene expression between sleeping animals and animals that are awake indicate that some of the key functions of sleep for brain are likely to be the following: homeostasis of synaptic connections; macromolecule biosynthesis, i.e., the brain synthesizes new molecules in readiness for the next period of wakefulness. Moreover, these studies show that sleep loss (sleep deprivation) leads to cellular stress not only in brain but in peripheral organs. New genetic mechanisms regulating sleep are being elucidated by these studies. In humans, we know that many aspects of sleep are heritable: timing of sleep, sleep duration and response to sleep deprivation. Most common sleep disorders are also heritable. Progress has been made in elucidating the gene variants increasing risk for restless legs syndrome and narcolepsy using genome-wide association studies. Rare genetic variants with large effects have been identified that affect sleep duration and the timing of sleep.