The front and rear of collective cell migration

During collective migration, cells not only migrate in a coordinated manner but also migrate faster and in a more directed way than individual cells. The coordination and efficiency of collective migration relies on cellular interactions through soluble and contact-mediated signals.Leader cells, which are generally localized at the front of the migrating group, have specific molecular features and morphological characteristics, which are reinforced by the soluble and contact-mediated signals present in their microenvironment.Leader cells facilitate the directed migration of followers, directly by generating pulling forces and indirectly by modifying the composition and structure of the extracellular matrix.Intercellular contacts between collectively migrating cells involving several sets of membrane proteins induce a local inhibition of locomotion through the regulation of RHO GTPases. Contact inhibition of locomotion is an essential event that promotes the coordinated polarization of collectively migrating cells.Several lines of evidence have shown that the followers actively participate in the collective movement by communicating with one another and with the leaders, by generating forces and contributing to the generation of chemotactic gradients.