Microtubule-binding protein which directly binds tubulin and is involved in both polymerization and stabilization of microtubules. Through its action on microtubules, may participate to the refinement of axons by negatively regulating axonal and leading processes branching. Plays a crucial role in neuron polarization and migration in the cerebral cortex and the hippocampus. May regulate voltage-gated sodium channels transport and function. May also play a role in MAPK signaling.Smallwood P.M., Proc. Natl. Acad. Sci. U.S.A. 93:9850-9857(1996).Gecz J., Hum. Genet. 104:56-63(1999).Ross M.T., Nature 434:325-337(2005).