Information Transfer in the Mammalian Circadian Clock

From photosynthetic bacteria to man, organisms throughout evolution have evolved biological clocks to adapt better to the 24 h period of the solar day. In most mammalian cells a set of "clock" genes and proteins forms a regulatory network that produces oscillations with a circadian period ( ≈ 24 h). The endogenous rhythms within the pacemaker, the suprachiasmatic nucleus (SCN) of the hypothalamus, are entrained by the light-dark cycle. The SCN sends synchronization signals to peripheral organs by hormone secretion sympathetic enervation and probably indirect means such as temperature regulation or feeding behavior. In our project we will analyze the information transfer from the environment via SCN neurons to physiological and metabolic processes. We will quantify the variability of light input, of neuronal oscillations and of activity rhythms using Shannon-entropies and mutual information. Promoters of clock-controlled genes will be analyzed with entropy- and affinity-based techniques. Moreover, we will study a synthetic circadian input-output system based on temperature driven cell cultures.