Axon guidance is an important process to insure
correct wiring of the nervous system in development. As an extending neuronal
axon navigates to its target, the trajectory is outlined by its responses to
different environmental cues. Because neuronal regeneration is, to a certain
extent a recapitulation of development, understanding the mechanism of axon
guidance will not only help delineate the pathoetiology of various neurological
disorders due to erroneous axon pathfinding but also shed light on potential
ways of clinical treatment of injured nervous system. Growing number of guidance
molecules like fasciclin, NCAM, L1-CAM, netrins, ephrins, slit, and semaphorins
have been identified as key players in the arena. Together with their
interacting partners, these molecules may serve as attractive or repulsive cues,
acting locally or at a distance to attain proper patterning of the nervous
system. Our team is currently focusing on a
novel family of axon guidance molecules called plexin. Members of this family
have been implicated in mediating growth cone collapsing signal of semaphorins,
though the underlying signaling mechanism remains unclear. Evidence has also
suggested that plexins are likely to subserve other physiological functions in
addition to axon pathfinding. In vitro functional studies, in
vivo overexpression and targeted disruption of plexins in transgenic mice
will allow better understanding of their physiological significance.