Septin1 is required for spindle assembly and chromosome congression in mouse oocytes

The bipolar spindle is a complex molecular machinery that drives chromosome congression and segregation. During meiosis in the mouse multiple microtubule organizing centers aggregate to form a bipolar intermediate followed by elongation and establishment of the barrel-shaped acentriolar meiotic spindle. Previous studies have shown that septin1 is localized to spindle poles in mitosis, suggesting its possible involvement in spindle assembly. We, therefore, asked whether perturbation of septin1 will impair the process of spindle assembly and investigated localization and function during mouse oocyte meiotic maturation. Septin1 was localized to the spindle at metaphase and at the midbody during cytokinesis. Disruption of septin1 function using siRNA caused a decrease in PBE and extensive spindle defects. Moreover, the process of chromosome congression was impaired. However, septin1 depletion did not cause aneuploidy in oocyte with an extruded polar body. Taken together, our results show that septin1 is a key player in spindle assembly and chromosome congression in mouse meiosis.