Vimentin bridges scales to convert polarized cell locomotion into coordinated collective migration.

Collective cell migration is central in development and disease. Vimentin is an intermediate filament protein expressed by epithelial cells at the edge of wounds where collective cell migration is most efficient. Yet, its functional role in this context remains underexplored. Here, we show that vimentin, overexpressed in cells undergoing partial epithelial-to-mesenchymal transition at the edge of epithelial monolayers, has a multiscale impact on the whole monolayer mechano-dynamics. Vimentin knockdown delays wound closure and reduces cell coordination, while increasing traction forces exerted by cells on the substratum. It also disrupts the directionality of leader cell migration, as well as the cohesion and coordinated motion of cells deep in the monolayer. We further show that vimentin promotes the conversion of polarized cell locomotion into coordinated collective migration by polarizing actin, focal adhesions, and traction forces, sustaining leader cells' lamellipodium protrusive activity and directionality, while allowing mechanical coupling of leader with follower cells. Altogether, we show that vimentin is essential for bridging polarized single-cell locomotion and coordinated collective migration to allow efficient collective migration.