Cell Dynamics in Early Embryogenesis and Pluripotent Embryonic Cell Lines: From Sea Urchin to Mammals

From oogenesisthrough fertilization and gastrulation, embryos use various mechanisms to regulate cell expansion, keeping a strict balance between cell proliferation, cell differentiation and cell death. While rapid divisions are necessary at the initial stage to ensure early embryo survival, further developmental transitions are marked by changes in cell cycle and transcriptional regulation. Pluripotency and capability of self-renewal are maintained in a low percentage of cells, the embryonic stem cells(ESCs), which will be later used as a cellular source for tissue replacement. Clearly, some essential characteristics of cell cycle and transcriptional regulationof the early embryo will be conserved in ESC lines. We addressed here the peculiarities of these developmental programs in early embryos and pluripotent embryoniccell lines, considering examples from marine invertebratesto mammals. Finally, we discussed the importance of transcription regulationand chromatin remodellingand their peculiar features in embryoniccells from these species.