A sleep bad night is enough to put everyone in a bad mood, and although scientists have long suspected a link between mood and sleep, molecular basis of this connection has remained a mystery. Now, new research has found several rare genetic mutations in the same gene that permanently connect the two.
sleep goes hand in hand with the mood. People suffering from depression and mania, for example, have frequently changed sleep patterns, such as those with seasonal affective disorder (SAD). And although no one knows exactly how these changes come about, in people with SAD are affected by changes in light exposure, the time to cue keeping the brain. But the mood affects sleep, sleep affects mood, or is it a third factor influencing both? Although a number of tantalizing leads have linked the circadian clock in the mood, there is "no definitive factor that prove causality or indicates the direction of the relationship," said Michael McCarthy, a neurobiologist at the Medical Affairs Center San Diego veterans and the University of California (UC), San Diego.
to see if they could establish a link between the circadian clock, sleep and mood, scientists in the new study examined the genetics of a family that suffers from abnormal sleep patterns and mood disorders, including SAD and something called advanced sleep phase, a condition in which people wake up early and sleep earlier than normal. the scientists screened the family of mutations in key genes involved in circadian clock, and identified two rare variants of PERIOD3 ( PER3 ) gene in members suffering from SAD and advanced sleep phase. "We found a genetic change in people who have both seasonal affective disorder and the morning lark trait," said lead researcher Ying-Hui Fu, a neuroscientist at UC San Francisco. When the team tested for these mutations in DNA samples from the general population, they found that they were extremely rare, occurring in less than 1% of samples.
Fu and his team then created mice that carried the gene variants novel. These transgenic mice showed an unusual sleep-wake cycle and struggled less when handled by the researchers, a typical sign of depression. They also had lower levels of PER2, a protein involved in circadian rhythms, the mice not mutated, providing a molecular explanation possible for unusual sleeping habits in the family. Fu said this supports the link between PER3 changes and both sleep and mood. " PER3 'role in the regulation of mood has never been demonstrated directly before," she said. "Our results indicate that PER3 might work to help us adjust to seasonal changes," altering the body's internal clock.
To further investigate, the team studied mice lacking a functional PER3 gene. They found that these mice showed symptoms of SAD, with a more severe depression when the duration of the simulated natural light in the laboratory has been reduced. Because SAD affects between 2% and 9% of people in the world, the new variants can not fully explain. But understanding the function of PER3 could provide insight into the molecular basis of a wide range of sleep disorders and mood, Fu said.
Together, these experiments show that PERIOD3 gene likely plays a key role in regulating the sleep-wake cycle, influencing the mood and regulation of the relationship between depression and seasonal changes in light availability, the team reports today in the Proceedings of the national Academy of sciences . "The identification of a mutation in PER3 with such an effect on mood is remarkable," McCarthy said. "It suggests an important role for the circadian clock in determining mood. "
the next step will be to analyze these results generalize to other people with mood and sleep disorders." It will be interesting to see if other rare variants in PER3 are, or SAD is constantly observed in other carriers, "McCarthy said. This could eventually lead to new drugs that selectively target the gene, McCarthy said," could be a strategy to deal mood or sleep disorders. "
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