Astrin/MAP126 has been identified as a mitotic spindle-associated protein essential for centrosome integrity and the progression through mitosis. Astrin/MAP126 interacts with Ninein and Aurora-A at the centrosome. Ninein, but not Aurora-A, appears to be required for proper localization of Astrin/MAP126 to the centrosome during S and G2 phase. A pool of Astrin/MAP126 also localizes to the outer kinetochore where it plays an essential role in chromatid adhesion and chromosome congression and segregation. The localization of Astrin/MAP126 to the spindle pole and kinetochore has been shown to be dependent on its phosphorylation by glycogen synthase kinase 3beta (GSK3beta).