Attachment/detachment of cortical myosin regulates cell junction exchange during cell rearrangement

Epithelial cells remodel cell adhesion and change their neighbors to shape a tissue. This cell rearrangement proceeds in three steps: the shrinkage of a junction, exchange of junctions, and elongation of the newly generated junction. Herein, by combining live imaging and physical modeling, we showed that the formation of myosin-II (myo-II) cables around the cell vertices underlies the exchange of junctions. The local and transient detachment of myo-II from the cell cortex is coupled with the junction shrinkage and elongation via an interplay between the LIM domain-containing protein Jub and the tricellular junction protein M6. Furthermore, we developed a mechanical model based on the wetting theory and clarified the way by which the physical properties of myo-II cables are integrated with the junction geometry to induce the transition between the attached and detached states and support the unidirectionality of cell rearrangement. Collectively, the present study elucidates the orchestration of geometry, mechanics and signaling for exchanging junctions.