Abstract: Correct meiotic spindle assembly in mammalian oocytes is crucial for ensuring accurate chromosome separation during meiosis.Transferring a complete set of chromosomes to daughter cells during cell division is essential for development and tissue homeostasis.Abnormal assembly of bipolar spindles often cause chromosomal missegregation,which in turn can easily lead to natural miscarriage and chromosomal birth defects.Therefore,exploring the mechanism of spindle assembly is necessary for understanding the process of meiosis.In somatic cells,mitotic spindle assembly is mediated by the centrosome acting as the microtubule organizing center.However,mammalian oocytes lack typical centrosomes and rely on other pathways such as microtubule organizing centers (MTOC) to assemble spindle.Although many components and pathways contributing to spindle assembly have been described,the assembly and functional mechanisms of acentriolar spindle still need to be improved.This review introduces the process of acentriolar spindle assembly in mammalian oocytes,and focus on the molecular mechanisms involved in microtubule nucleation,spindle polarization and elongation,chromosome arrangement and separation,as well as the role of spindle checkpoint (SAC) in spindle assembly.In addition,the mechanism by which chromosomes and actin filaments participate in spindle assembly during meiosis is also discussed in this review,aiming to provide reference for the study of bipolar spindle assembly and chromosome separation mechanisms in mammalian oocytes.

Key words: meiosis; spindle sssembly; chromosome segregation; aMTOC