The liver by day and by night

Circadian clocks oscillate over a period of ≈24 h in light-sensitive organisms and coordinate a wide variety of behavioral, physiological, and molecular functions with geophysical time. In mammals, clocks are present in virtually every cell of the body and function in a cell autonomous and self-sustained manner. The molecular clockwork relies on transcription-translation feedback loops, which generate self-sustained oscillations in the expression levels of the clock components (e.g. PERs, CRYs, CLOCK, BMAL1, NR1D1,2, RORs). These oscillations further control downstream processes through transcriptional and post-transcriptional regulation.