Oscillations can be seen in gene expression patterns of individual fibroblasts.

SCHIBLER/ELSEVIER

Every cell in the body has its own little clock, according to Emi Nagoshi, Ueli Schibler (University of Geneva, Switzerland), and colleagues. These peripheral clocks may be closely related to the body's central clock—the suprachiasmatic nucleus (SCN).

Neurons of the SCN maintain circadian gene expression for long periods of time. Other cells, however, were thought to rely on the SCN to maintain their oscillations, as the amplitude of gene expression oscillations in fibroblast cultures lessens rapidly with time in culture. But Schibler's group shows that the examination of mass cultures masks the continued ability of each cell to maintain strong oscillations.

By looking at individual fibroblasts, the authors were able to see persistent oscillations. Even after mitosis, daughter cells continued the rhythm of the mother, although with a slight phase shift, probably due...

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