Health

An internal clock hidden in human skin cells could reveal whether your body clock is out of sync with your lifestyle, say researchers.

Steven Brown of the University of Zurich in Switzerland and his colleagues knew that the brain's circadian clock causes a gene called Bmal1 to be more active in the body's other cells during the daytime.

To find out how closely matched this activity was, they used a virus to equip skin cells taken from 11 early-rising people dubbed "larks" and 17 late-rising "owls" with a firefly gene that would produce a visible glow whenever Bmal1 was active. "The result is light coming out of the cell in a 24-hour rhythm," says Brown.

By monitoring the 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.

There were discrepancies too, however, most notably in three individuals with seasonal affective disorder. This suggested that skin biopsies might be useful for diagnosing sleep and circadian disorders.

"Knowing that skin clocks ‘tick' 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," says Russell Foster, a circadian rhythm specialist at the University of Oxford, UK.

"It's remarkable that measures from the skin allow predictions of brain-driven behaviour," he adds.

Journal reference: Proceedings of the National Academy of Sciences (DOI: 10.1073/pnas.0707772105)

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