Isolation and manipulation of meiotic spindles from mouse oocytes reveals migration regulated by pulling force during asymmetric division.

Spindles are essential for accurate chromosome segregation in all eukaryotic cells. This study presents a novel approach for isolating fresh mammalian spindles from mouse oocytes, establishing it as a valuable model system for a wide range of possible studies. Our method enables the investigation of the physical properties and migration force of meiotic spindles in oocytes. We found that the spindle length decreases upon isolation from the oocyte. Combining this observation with direct measurements of spindle mechanics, we examined the forces governing spindle migration during oocyte asymmetric division. Our findings suggest that the spindle migration is regulated by a pulling force and a net tensile force of approximately 680 pN is applied to the spindle during the migration process. This method, unveiling insights into spindle dynamics, holds promise as a robust model for future investigations into spindle formation and chromosome separation. We also found that the same approach could not isolate spindles from somatic cells, indicative of mammalian oocytes having a unique spindle organization amenable to isolation.