AXON GUIDANCE TO AND FROM CHOICE POINTS

Significant progress has been made recently in understanding axon guid ance to and from choice points. Netrins have been shown to function as conserved midline chemoattractants in vertebrates and insects, and re ceptors for netrins and semaphorins/collapsins have been identified. M ore evidence has accumulated that repulsion plays a key role in guidan ce, including the involvement of the ephrin/Eph receptor system in con tact repulsion.