Microtubule-binding protein which stabilizes dynamic microtubules by slowing growth and shrinkage at both plus and minus ends and serves as a sensor of microtubule damage, protecting microtubules from the microtubule-severing enzyme SPAST (By similarity). Induces microtubule branching which is mediated by the formation of long SSNA1 fibrils which guide microtubule protofilaments to split apart from the mother microtubule and form daughter microtubules (By similarity). Plays a role in axon outgrowth and branching (By similarity). Required for cell division (By similarity). Self-associates to form fibrils. Also forms dimers as well as monomers. Interacts with SPAST. In sperm, strongly expressed in the basal body region with weaker expression in the axoneme (By similarity). Localizes to axon branching points in neurons (By similarity). Belongs to the SSNA1 family.