Human oocytes are prone to assembling meiotic spindles with unstable poles, which can
favor aneuploidy in human eggs. The underlying causes of spindle instability are unknown.
We found that NUMA (nuclear mitotic apparatus protein)–mediated clustering of microtubule
minus ends focused the spindle poles in human, bovine, and porcine oocytes and in mouse
oocytes depleted of acentriolar microtubule-organizing centers (aMTOCs). However, unlike
human oocytes, bovine, porcine, and aMTOC-free mouse oocytes have stable spindles. We …