GAPs in Slit-Robo signaling.

Neuronal migration requires the integration of a number of diverse environmental cues and subsequent translation to specific responses such as directed cytoskeletal remodeling. Accurate knowledge of the signal transduction pathways linking activation of surface receptors to actin dynamics is necessary in order to understand the regulation of such processes. Activation of the Roundabout (Robo) receptor mediates a repulsive response in certain pioneering axons and migratory neurons. Recently, Wong et al have described a signaling link between Robo activation and specific GTPase activity that appears to regulate neuronal migration. A novel family of GTPase regulators, responsive to Slit-Robo engagement, has been identified and convincingly shown to alter the migration of neuronal cells. This study not only delineates a specific signaling route from guidance receptors to directed neuronal movement, but also offers clues towards potential regulatory mechanisms that ensure specificity of the Slit-Robo response.