Microtubule-binding protein which directly binds tubulin and is involved in both polymerization and stabilization of microtubules (By similarity). Through its action on microtubules, may participate in the refinement of axons by negatively regulating axonal and leading processes branching (By similarity). Plays a crucial role in neuron polarization and migration (By similarity). Regulates voltage-gated sodium channels transport and function (By similarity). Required for proper head development, it is involved in neural differentiation through regulation of the mek5-erk5 pathway (PubMed:17584734). Not secreted. Localizes to the lateral membrane and intercalated disks of myocytes. Expressed maternally. Zygotic expression is observed at neurula and tailbud stages. Widely expressed in the presumptive ectoderm during blastula, and in the dorsal structures during neurula and tailbud stages. At tailbud stages, strongly expressed in the ventral region of neural tube. Isoform 1 is expressed weakly at neurula and strongly at tailbud stage. Isoform 2 and isoform 3 are strongly expressed at the tailbud stage. Belongs to the heparin-binding growth factors family.