Collective cell migration mediates the tissue rearrangements necessary for embryonic development. Cells migrating collectively experience asymmetric intercellular forces and require intercellular contacts to be maintained. However, although the cadherin cell–cell adhesion molecules are able to respond to mechanical force, little is known about the significance of mechanosensing in collective cell migration. Weber et al. now report that the mechanical response of cadherins mediates polarization and directed collective migration of Xenopus laevis mesendoderm cells (Dev. Cell 22, 104–115; 2012).

The authors applied force to individual mesendoderm cells adhering to cadherin-coated magnetic beads and observed cell polarization, directional migration and re-organization of keratin intermediate filaments (KIFs). These behaviours required keratin and plakoglobin, a protein that interacts with cadherins and intermediate filaments, as shown using cells from keratin- and plakoglobin-depleted embryos. In assays of two cells adhering to each other on traction permissive matrices, the authors demonstrated that force application recruited plakoglobin to cadherin adhesions, and that plakoglobin was able to reorganize KIFs and link keratin to the mechanosensitive cadherins. Finally, visualization of Xenopus embryos during gastrulation showed that plakoglobin and keratin were also needed for mesendoderm polarity and migration in vivo. The identification of this mechanoresponsive cadherin pathway highlights the important roles of forces in orchestrating collective cell migration.