Cell and tissue-autonomous development of the circadian clock in mouse embryos.

The emergence of the circadian rhythm is a dramatic and physiologically essential event for mammals to adapt to daily environmental cycles. It has been demonstrated that circadian rhythms develop during the embryonic stage even when the maternal central pacemaker suprachiasmatic nucleus has been disrupted. However, the mechanisms controlling development of the circadian clock are not yet fully understood. Here, we show that the circadian molecular oscillation in primary dispersed embryonic cells and explanted salivary glands obtained from mPER2(Luc) mice embryos developed cell- or tissue-autonomously even in tissue culture conditions. Moreover, the circadian clock in the primary mPER2(Lu)(c) fibroblasts could be reprogrammed by the expression of the reprogramming factors. These findings suggest that mammalian circadian clock development may interact with cellular differentiation mechanisms.