Biology

Dr. Michael Smutny
Institute of Science and Technology Austria

During embryonic development, mechanical forces are essential for driving cellular rearrangements and global tissue shape changes. We show that in the early zebrafish embryo, forces are generated at the interface between two neighboring tissues, namely the axial mesoderm (prechordal plate) and the overlying (neur)ectoderm, which are pivotal for positioning the prospective forebrain during gastrulation. During this process, which requires E-­cadherin-­mediated cell-­cell adhesion, collective migration of mesoderm cells towards the animal pole leads to global rearrangement of cells within the ectoderm, which move towards the opposing vegetal pole of the embryo. We demonstrate experimentally that the speed ratio between mesoderm and ectoderm cell movements determines the coupling strength and resultant direction of tissue movements. Using a theoretical framework based on hydrodynamic tissue behavior, we infer that friction forces are generated between those tissues, which are critical for long-­range force transmission within the ectoderm.

Our data thus establish the emergence of friction forces at the interface between moving tissues as a critical force-­generating process shaping the embryo.