Early sorting events in the mouse embryo

How cells in mouse blastocyst sort themselves out to generate the inner cell mass, and how the embryos respond to manipulation during early development remain unexplained. Previous studies have indicated the importance of differential cell adhesion or oriented cell division along an apical–basal axis in the sorting phenomenon. Jean-Léon Maître et al. use a combination of biophysical measurement, modelling and both genetic and experimental manipulation of contractile components to analyse inner cell mass formation in the early mouse embryo. They suggest that cell polarization generates cells of different contractilities, which trigger their sorting to inner and outer position. The contractile forces are shown to modulate the sub-cellular localization of Yap, a transcriptional regulator known to influence cell fate.