Local Ras/actin signaling orients individual pseudopods in shallow gradients

Eukaryotic cells navigate effectively in very shallow chemotactic gradients.The issue is how cells analyze such dim signals.Experiments suggest that cells extend pseudopods with a directional bias imposed by the local concentration of chemoattractant (1, 2).Alonso et al. (3) describe a simple mechanism for local signaling, based on earlier work by Andrew and Insall (1) on pseudopod splitting: The extending pseudopod splits into two pseudopods, of which one is retracted and the other becomes dominant.The local gradient stabilizes the pseudopod that is extended toward the