Accurate chromosome segregation during meiosis is crucial for reproduction. Human and porcine oocytes transiently cluster their chromosomes before the onset of spindle assembly and subsequent chromosome segregation. The mechanism and function of chromosome clustering are unknown. Here we show that chromosome clustering is required to prevent chromosome losses in the long gap phase between nuclear envelope breakdown and the onset of spindle assembly, and to promote the rapid capture of all chromosomes by the acentrosomal spindle. The initial phase of chromosome clustering is driven by a dynamic network of Formin-2- and Spire-nucleated actin cables. The actin cables form in the disassembling nucleus and migrate towards the nuclear centre, moving the chromosomes centripetally by interacting with their arms and kinetochores as they migrate. A cage of stable microtubule loops drives the late stages of chromosome clustering. Together, our data establish a crucial role for chromosome clustering in accurate progression through meiosis.

减数分裂过程中准确的染色体分离对于繁殖至关重要。人类和猪的卵母细胞在纺锤体组装和随后的染色体分离开始之前短暂地聚集其染色体。染色体聚类的机制和功能尚不清楚。在这里，我们表明，需要染色体聚类来防止核膜破裂和纺锤体组装开始之间的长间隙阶段的染色体丢失，并促进心体纺锤体快速捕获所有染色体。染色体聚类的初始阶段是由 Formin-2 和 Spire 有核肌动蛋白缆的动态网络驱动的。肌动蛋白缆在分解的细胞核中形成，并向核中心迁移，在迁移时通过与染色体臂和着丝粒的相互作用使染色体向心移动。稳定的微管环笼驱动染色体聚类的后期阶段。总之，我们的数据确定了染色体聚类在减数分裂准确进展中的关键作用。