Research Points Finger at Genes for Feeling Sleepy

by Medindia Content Team on Oct 19 2007 2:10 PM

Ever wonder why you just love to sleep? Well, researchers say that the answer may lie in your genes.

The researchers made the suggestion after finding that the genes responsible for the 24 hour body clock influence not only the timing of sleep, but also appear to be central to the actual restorative process of sleep.

"We still do not know why we benefit from sleep, or why we feel tired when we are 'lacking' sleep, but it seems likely that sleep serves some basic biological function for the brain such as energy restoration for brain cells or memory consolidation," said Dr Bruce O'Hara of the University of Kentucky, one of the neuroscientists on the study.

"We have found that clock gene expression in the brain is highly correlated to the build-up of sleep debt, while previous findings have linked these genes to energy metabolism. Together, this supports the idea that one function of sleep is related to energy metabolism," he added.

As a part of the study, boffins led by Dr. Paul Franken of Stanford University and Lausanne University conducted a study on a mouse model in which they utilized three inbred strains of mice with different genetic make-ups that had previously been shown to differ in their response to sleep deprivation.

In this study, mice were first sleep deprived during the daytime period when mice normally sleep then allowed recovery sleep. Changes in gene expression for three clock genes were examined throughout the brain during both phases. The researchers noted that the more the mice were kept awake the clock gene expression generally increased. When sleep was allowed, the clock gene expression generally decreased.

This supported the theory that these genes play a role in the regulation of the need for sleep. Generally, the expression of the clock-genes Period-1 and Period-2, increased at a faster rate in mouse strains with the poorest quality of recovery sleep suggesting that the detailed dynamic changes in expression may underlie individual differences in sleep length and sleep quality. The changes in gene expression were also shown to occur in many different brain regions supporting the idea that sleep is a global brain function.

A handful of genes such as Period-1 and Period-2 have been shown previously to underlie our circadian rhythms i.e. behaviour and physiology that follow a 24 hour cycle. Circadian rhythms allow animals and plants to predict and prepare for periodic changes in the environment. The anticipatory increase in clock-gene expression may be, on a molecular level, an animal's preparation for activity.

As shown in this study, the clock genes' role in direct sleep regulation may also influence sleep duration and human performance with differing amounts of sleep. The research could also help shed light on the biology of mood disorders, such as Seasonal Affective Disorder (SAD) or bipolar disorder, that appear linked to both sleep and circadian rhythms.

The research is published online open access journal BMC Neuroscience.