Abstract The spindle apparatus is essential for both mitotic and meiotic cell division. Contrast to mitotic counterpart, meiotic spindle of mammalian oocytes is lack of centrosomes, thus relying on acentrosomal microtubule organizing centers (aMTOCs) to assemble the spindle. In addition, the positioning of spindle in oocytes is mediated by F-actin network, not the astral microtubules (MTs). Overall, the role of astral MTs in meiotic spindle positioning has been overlooked, due to the lack of centrosomes. In this study, we presented an optimized method for staining and super-resolution imaging of astral MTs during meiosis. Though lacking centrosomes, both interpolar and astral MTs were present in the spindle through meiosis. The growth of astral MTs was inhibited by CDK1 and Arp2/3. The premature extension of astral MTs at metaphase I impaired the positioning of meiotic spindle, resulting in symmetric division of oocytes after meiosis I. Collectively, these results provide novel insights on the regulation of astral MT growth to facilitate the positioning of meiotic spindle in oocytes.
Li et al. (Thu,) studied this question.