Mechanosensitive dynamics of lysosomes along microtubules regulate leader cell emergence during collective cell migration

Collective cell migration during embryonic development, wound healing, and cancer metastasis requires the emergence of leader cells at the migration front. Despite their physiological relevance, the full mechanisms underlying the emergence of leader cells remain elusive. Here we report that leader cells display a peripheral accumulation of lysosomes in diverse model systems for wound healing, including cultured epithelial monolayer, mouse embryonic skin, and Drosophila embryos. This accumulation involves cellular contractile forces driving lysosomal transport along microtubules towards the leading edge. Indeed, we control leader cell emergence by manipulating lysosomal movement on microtubules. We further find that peripheral lysosomes associate with Rac1 molecules at the leading periphery, regulating local Rac1-activity, triggering actin polymerization and promoting lamellipodium formation. Taken together, we demonstrate that beyond their catabolic role, lysosomes act as an intracellular platform that links mechanical and biochemical signals to control the emergence of leader cells. During collective migration, only a few cells become leaders that guide tissue movement. Here, the authors show that contractile forces drive lysosomes to the cell edge, where they activate Rac1 and trigger leader cell emergence.