Border cell migration during Drosophila oogenesis is a potent model to study collective cell migration, a process involved in development and metastasis. Border cell clusters adopt two main types of behaviour during migration: linear and rotational. However, the molecular mechanism controlling the switch from one to the other is unknown. Here, we demonstrate that non-muscle Myosin II (NMII, also known as Spaghetti squash) activity controls the linear-torotational switch. Furthermore, we show that the regulation of NMII takes place downstream of guidance receptor signalling and is critical to ensure efficient collective migration. This study thus provides new insight into the molecular mechanism coordinating the different cell behaviours in a migrating cluster.

Collective cell migration is a critical mechanism involved in cell movement during various physiological and pathological processes such as angiogenesis and metastasis formation. During collective movement, cells remain functionally connected and can coordinate individual cell behaviors to ensure efficient migration. A cell-cell communication process ensures this complex coordination. Although the mechanisms regulating cell-cell communication remain unclear, recent findings indicate that it is based on acto-myosin cytoskeleton tension transmission from cell to cell through adherens junctions. As for single cell migration, small GTPases of the Rho and Rab families have been shown to be critical regulators of collective motion. Here, we discuss our current understanding on how these small GTPases are themselves regulated and how they control cell-cell communication during collective migration. Moreover, we also shed light on the key role of cell-cell communication and RhoGTPases in the physiological context of endothelial cell migration during angiogenesis.