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Figure 7. Here we speculate on the possible interactions between cell autonomous circadian and somite oscillator components during somite formation and differentiation. The somite and circadian clocks both consist of negative feedback loops requiring the transcriptional activation (BMAL1, CLOCK) and repression (HES6/7, HER1; PERIOD1/2, CRY1/2) of clock components. The period of the somite clock is thought to be regulated by the balance of bHLH transcription factors present in the cell (“dimer cloud”) [13]. Bmal1 may upset the balance by hetero-dimerizing with proteins in the dimer cloud (HES6/7, HER1) or by competing with HES6/7/HER1 for binding to the H-box (green arrow). NOCTURNIN may also impact the balance of proteins present in the dimer cloud by inhibiting translation of dimer cloud components (red line). BMAL1-CLOCK heterodimers are known to positively activate genes involved in myogenesis (MyoD, MRF5). Perhaps, NOCTURNIN inhibits translation of repressors of myogenesis (blue arrow). We hypothesize that phosphorylation of CREB protein (CREB-P) may also act to coordinate components of the circadian and somite clock. doi:10.1371/journal.pone.0108266.g007 Image published in: Curran KL et al. (2014) Image reproduced on Xenbase with permission of the publisher and the copyright holder. This image is reproduced with permission of the journal and the copyright holder. This is an open-access article distributed under the terms of the Creative Commons Attribution license Larger Image Printer Friendly View

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