Microtubule-associated protein involved in the stabilization of microtubules along the axis of migration during radial intercalation. Promotes the establishment and stabilization of an axis of microtubules required for the active migration of cells into the outer epithelium (By similarity). Microtubule-associated protein that promotes microtubule bundling and stabilizes microtubules against depolymerization in response to cold shock (By similarity). Essential for ciliary central apparatus formation which requires both its microtubule-binding and bundling activities and for ciliary localization of HYDIN and SPAG6 in ependymal cilia (By similarity). Binds actin in intestinal epithelial cells (IECs), essential for IECs survival and contributes to formation of filopodia and lamellipodia in migrating IECs (PubMed:31473225). Regulates planar cell polarity signaling pathway and asymmetric microtubule accumulation in ciliated epithelia (By similarity). {ECO:0000250|UniProtKB:Q0IH24, ECO:0000250|UniProtKB:Q99JL1, ECO:0000269|PubMed:31473225}. This is the function of SPEF1 (sperm flagellar and cilia associated 1, ENSG00000101222).