Microscale matrix defects suppress tension-dependent protrusions and stall collective cell migration.

During development, wound repair, and disease, epithelia must detect and respond to subtle extracellular defects to maintain coordinated migration. We show that collectively migrating epithelia undergo large-scale spatiotemporal stalling in response to laser-ablated micro-defects in the presence of collagen type IV. When the filopodia of leading-edge cells encounter micro-defects, the resulting local cytoskeletal disruption propagates to the follower cells, producing multicellular stalling over length scales much larger than the original defect. Extracellular changes in matrix stiffness, collagen type, and osmolarity regulate cell stiffness and membrane tension, which, in turn, control protrusive activity and stall migration. Through these extracellular variations, we found that stiffer cells and lower membrane tension suppress protrusions in leader cells, which enhances multicellular stalling through intercellular propagation of cytoskeletal disruption. This work advances the biophysical understanding of cell migration by showing that collagen-IV, softer matrices, and hypertonic media enhance cellular sensing of extracellular defects and wounds.