NUMA1 (nuclear mitotic apparatus protein 1) is a microtubule-binding protein that plays essential roles in mitotic spindle organization and chromosome 11. Its primary function involves tethering microtubule minus ends at spindle poles, which is critical for establishing and maintaining proper spindle structure during cell division 1. NUMA1 regulates mitotic spindle orientation through interaction with the dynein-dynactin complex and cortical proteins including GPSM2 and G(i) alpha proteins. During mitosis, NUMA1 is phosphorylated by CDK1 and PLK1 kinases, and this phosphorylation is required for proper spindle function and orientation 2. The protein also facilitates spindle positioning through dynamic interactions with EB1 and astral microtubules 3. Beyond mitosis, NUMA1 has been identified as a structural component of the nuclear matrix and plays a role in axon initial segment assembly by inhibiting endocytosis of key proteins like neurofascin-186 4. Clinically, NUMA1 is relevant as an autoantigen target, with anti-NUMA1 antibodies associated with connective tissue diseases including Sjögren's syndrome and systemic lupus erythematosus 5. Additionally, NUMA1 upregulation has been implicated in chemotherapy resistance in ovarian cancer through DNA repair pathway enhancement 6.