AN INTERNAL clock hidden in your skin cells could reveal whether your body clock is out of sync with your lifestyle.
Steven Brown of the University of Zurich in Switzerland and his colleagues knew that the brain鈥檚 circadian clock causes a gene called Bmal1 to be more active in peripheral cells during the daytime. To find out how closely matched this activity was, they used a virus to equip skin cells from 11 early-rising 鈥渓arks鈥� and 17 late-rising 鈥渙wls鈥� with a firefly gene that would produce a visible glow whenever Bmal1 was active. 鈥淭he result is light coming out of the cell in a 24-hour rhythm,鈥� says Brown.
By monitoring times when the cells glowed, they demonstrated that skin cells showed the same sleep-wake patterns as those reported in questionnaires by at least half the donors. But there were discrepancies too 鈥� most notably in three individuals with seasonal affective disorder, suggesting that skin biopsies might be useful for diagnosing sleep and circadian disorders (Proceedings of the National Academy of Sciences, ).
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鈥淜nowing that skin clocks 鈥榯ick鈥� in the same way as brain clocks provides a nice tool to address whether a person is likely to be an early or late riser,鈥� says Russell Foster, a circadian rhythm specialist at the University of Oxford. 鈥淚t鈥檚 remarkable that measures from the skin allow predictions of brain-driven behaviour.鈥�
