Mechanical-molecular interplay underlying the self-organized patterning of the early embryo. – ForcePattern

Mechanical forces play an essential role in embryonic development, most evidently as the drivers of morphogenesis, but also as short- and long-range signals contributing to self-organized patterning. Whereas the role of mechanics in cell fate specification has long been demonstrated in vitro, how mechanical and molecular cues combine in vivo to dynamically pattern initially naïve fields of cells remains a challenge. This is in part because of the technical and conceptual obstacles to overcome to characterize and disrupt the mechanical underpinnings of a given developmental process. Here, taking advantage of quail embryos great amenability to dynamic approaches and mechanical perturbations, we propose to investigate how mechanical forces pattern cell fate in live embryos. First, we will elucidate how the force of gravity, known break the original radial symmetry, acts on the avian epiblast to position the anteroposterior axis. Second, we will investigate how this symmetry-breaking information provides a rough prepattern that is then reinforced through mechanical feedback. In particular we will test whether the emergent tissue mechanics create a mechanical niche that maintains the pluripotency state of embryonic cells. Third, we will explore how the mechanical and molecular cues, we have identified in avians, compare in the mouse embryo. Altogether these studies will decipher how mechanical forces break the original symmetry by specifying cell fate locally and how mechanical feedback on gene expression subsequently perpetuates the self-organized patterning in avian and mammal embryos.