11. Information Transfer in the Mammalian Circadian Clock

Most species evolved a circadian clock to adapt to the 24 h period of the solar day. In mammals, these clocks generate endogenous rhythms by regulatory gene networks in almost every cell. A pacemaker, the suprachiasmatic nucleus (SCN) as the master clock, receives environmental input and orchestrates peripheral organs via sympathetic enervation, temperature and humoral factors. However, the mechanisms by which this synchronization is achieved are largely unknown. In order to elucidate paradigms of environmental information transfer within the circadian network, we address the following questions: How is environmental information perceived by different circadian networks? Do different circadian networks vary in their responses to a given signal, and, if so, do the differences depend on inherent circadian properties? Which part of the signal (onset, offset, duration, strength) is relevant for the responses? To address these questions, we combine experimental data from cultured single cells and organotypic slices with mathematical models of circadian oscillators and find that temperature signals have a strong impact on circadian rhythms, depending on the specific circadian properties of the clock cells.