Zfhx3 is required for proper spindle assembly and chromosome segregation during oocyte meiosis I in mice

ZFHX3, a multifunctional transcription factor, plays pivotal roles in a variety of physiological and pathological processes, including neuronal differentiation, development, atrial fibrillation, and cancer. Notably, homozygous deletion of Zfhx3 is embryonic lethal, whereas its hemizygous deletion results in reduced neonatal body weight and increased preweaning mortality in mice. Also, a deletion mutation in Zfhx3 is significantly associated with reduced litter size, a key reproduction-related trait in goats, suggesting that ZFHX3 is involved in reproductive development. However, its specific function in female reproduction remains unclear. Given that oocyte meiosis is a fundamental process in female reproduction, we investigated the role of Zfhx3 in this process.

We performed siRNA microinjection, immunofluorescence staining, chromosome spreading, Western blotting and other experiments to investigate the function of Zfhx3 in mouse oocyte meiosis.

We found that Zfhx3 was present in both the nucleus and cytoplasm in GV oocytes and became predominantly localized to the cytoplasm after germinal vesicle breakdown. Knockdown of Zfhx3 caused failure of first polar body extrusion due to sustained activation of the spindle assembly checkpoint (SAC). Zfhx3-deficient oocytes were defective in spindle assembly, microtubule-kinetochore attachment, and chromosome segregation during meiosis I, resulting in aneuploidy in MII oocytes. These defects could be ameliorated by ectopic expression of Zfhx3 mRNA.

Our findings provide evidence for an essential role of Zfhx3 in spindle assembly and chromosome segregation during mouse oocyte meiosis I, and provide a mechanistic basis for its mutations in female reproductive disorders.