Developmental clock and mechanism of de novo polarization of the mouse embryo

Abstract

Timing and trigger of cell polarization During mammalian embryo development, the first cell fate decision separates the progenitors of the trophectoderm (destined to form the placenta) from the inner cell mass (which forms all tissues of the embryonic and yolk sac). A key event for this first lineage segregation is the establishment of apicobasal cell polarity. This event is set to occur at a fixed developmental stage. The factors that trigger the establishment of cell polarity as well as its temporal regulation have remained unknown. Zhu et al. show in mouse embryos that three molecular regulators—Tfap2c, Tead4, and RhoA—are sufficient to advance the timing of cell polarization with subsequent cell fate specification and morphogenesis. Science , this issue p. eabd2703