Axon guidance to and from choice points.

Significant progress has been made recently in understanding axon guidance to and from choice points. Netrins have been shown to function as conserved midline chemoattractants in vertebrates and insects, and receptors for netrins and semaphorins/collapsins have been identified. More evidence has accumulated that repulsion plays a key role in guidance, including the involvement of the ephrin/Eph receptor system in contact repulsion.