Signaling by Eph receptors and their ephrin ligands

What are the mechanisms by which Eph receptor tyrosine kinases guide axons and migrating cells? Recent results show that Eph receptors bind some of the well-known effector molecules that are implicated in the organization of the actin cytoskeleton; moreover, biochemical and genetic evidence suggests a signaling role for transmembrane ephrin ligands in axon pathfinding.