Multi-level Fgf4- and apoptosis-dependent regulatory mechanism ensures the plasticity of ESC-chimaeric mouse embryo

Abstract

The preimplantation mammalian (including mouse and human) embryo holds remarkable regulatory abilities, which have found their application for example in the preimplantation genetic diagnosis of human embryos. Another manifestation of this developmental plasticity is the possibility of obtaining chimaeras by combining either two embryos or embryos and pluripotent stem cells, which enables the verification of the cell pluripotency and generation of genetically modified animals used to elucidate gene function. Using mouse chimaeric embryos (constructed by injection of embryonic stem cells into the 8-cell embryos) as a tool, we aimed to explore the mechanisms underlying the regulatory nature of the preimplantation mouse embryo. We comprehensively demonstrated the functioning of a multi-level regulatory mechanism involving the FGF4/MAPK signalling as a leading player in the communication between both components of the chimaera. This pathway, coupled with the apoptosis, cleavage division pattern, and cell cycle duration controlling the size of ESC component and giving it a competitive advantage over host embryo blastomeres, provides a cellular and molecular basis for regulative development, ensuring the generation of the embryo characterised by proper cellular composition.

The salt-and-pepper pattern in mouse blastocysts is compatible with signaling beyond the nearest neighbors

“… 49 Apoptosis mostly starts occurring in mid blastocysts, and the rates steadily increase with increasing cell number. 8 , 50 Hence, apoptosis could only account for the discrepancy for mid blastocysts. Furthermore, our model would predict that apoptosis of one cell fate dominates over the other.…”