Molecular cues that guide the development of neural connectivity.

Diffusible and substrate-bound cues can guide axonal pathway choice via attractive and repulsive signals. A number of families of signalling molecules have been identified, including netrins and their receptors, semaphorins, neuropilins, Eph receptor tyrosine kinases, ephrins and CAMs. Many of these signalling molecules can have a dual role, functioning either as attractants or as repellents. Direction of growth cone extension requires reorganization of the cytoskeleton, which may be directed by the Rho family of GTPases.