Essential for the formation and stability of microtubules (MTs) (PubMed:16890222, PubMed:31409757). Required for the organization of the mitotic spindle and for the proper attachment of kinetochores to MTs (PubMed:25789526). Promotes the recruitment of NUDC to the mitotic spindle for mitotic progression (PubMed:25789526). {ECO:0000269|PubMed:16890222, ECO:0000269|PubMed:25789526, ECO:0000269|PubMed:31409757}. This is the function of EML4 (EMAP like 4, ENSG00000143924).