For whom the bells toll: Networked circadian clocks

Circadian cycles are robust and precise biological rhythms common in unicellular and multicellular organisms. Single cells have been shown to sustain autonomous near 24-h rhythms, however, many cells and tissues appear to require cell-cell interactions to maintain periodicity. This review highlights the mechanisms and benefits of coupling circadian oscillators. We focus on how populations of circadian oscillators synchronize in a variety of biological systems and describe recent efforts to model mathematically coupling and synchrony in the mammalian suprachiasmatic nucleus. We conclude by discussing the effects of disrupted circadian coupling on health and behavior.