jBillou edited Introduction.tex  about 9 years ago

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At the single-cell level, the circadian rhythm is carried out by a network of transcriptional and translational feedback loops that drive rhythmic expression of genes with a period of about 24 hours \cite{Buhr_2013}. This cell autonomous rhythm is self-sustained \cite{19956762} and is considered to temporally orchestrate many important cell physiological processes such as metabolism \cite{19286518} \cite{23303907}, redox balance and chromatin conformation \cite{24056944}.  The cell cycle can also be considered as a periodic process lasting on the order of one day in dividing mammalian cells \cite{19270522}. Consequently, is reasonable to expect that, when circadian and cell cycles run in parallel in the same cell, their coupling could lead to synchronization, also called mode-locking.   Evidences in mammalian cells \cite{17482552}, \cite{14963227} showed synchronization between circadian and cell cycles oscillators which is compatible with the 1:1 mode-locking state. Moreover, many studied described circadian rhythms of cell divisions or clock-dependent variations of mitotic indexes in different types of mammalian cells \cite{12934012}, \cite{23267082}, \cite{15914209}. These observations could be explained by a model denominated \texit{circadian gating of the cell-cycle}, defined as a control operated by the circadian clock that determines temporal windows in which certain cell cycle transitions are either allowed or restricted. Circadian coupling has been also demonstrated in lower organism such cyanobacteria, both, at the population \cite{8816773} and single-cell level \cite{Yang2010}, and in budding yeast \cite{19346485}. A deeper understanding of how the two biological systems interact is currently of great interest, notably to better understand the role of circadian clocks in proliferating tissues such as the epidermis, immune or stem cells and in cancer \cite{25589491} (ref). \cite{25589491}.  %\textit{Our previous findings}