Cell migration and invasion require the dynamic coordination of adhesion, actin organization, and membrane traffic at the leading edge of the cell. Similar processes are also involved in the migration of growth cones and in the establishment of synapses during neuronal development. Our major interest is the identification and the analysis of the molecular mechanisms coordinating the protrusive activity at the edge of migrating cells, and in developing neurons. We have identified molecular networks that are implicated in these processes. These networks include scaffold proteins, and regulators or effectors of small GTPases of the Rho and Arf families. By using both in vitro and in vivo approaches, we are aiming at characterizing fundamental cellular mechanisms underlying cell motility events relevant to both physiological and pathological conditions.