Mechanisms of acentrosomal spindle assembly and stability during oocyte meiosis

项目摘要 有性生殖的生物利用一种称为减数分裂的特殊细胞分裂程序来减少它们的繁殖。 染色体数目减半以产生单倍体配子。正确执行这一过程对于 成功怀孕，因为减数分裂染色体分离错误导致非整倍体（不正确 胚胎中的染色体数目），这是人类流产和出生缺陷的主要已知原因。 女性的减数分裂特别容易出错，这种脆弱性对人类健康有着深远的影响： 据估计，10-25%的人类胚胎染色体异常，这些缺陷中的绝大多数 由雌性减数分裂细胞（称为卵母细胞）的问题引起。尽管女性的重要性 减数分裂的成功繁殖和人类健康，令人惊讶的是，很少有人知道的机制， 以确保卵母细胞中染色体的准确分配。 卵母细胞具有一些特殊的特征，需要使用新的细胞分裂机制。也许 最重要的是，卵母细胞缺乏中心体，在其他细胞类型中，中心体定义和组织纺锤体极; 因此，这些细胞中的纺锤体必须使用不同的机制组装。利用C.作为一个模特，我们 先前证明，无中心体纺锤体组装通过1）核化/稳定化 2）微管的分类，使它们的负 末端位于阵列的外围，3）将这些末端组织成初生极，以及4） 这些位点的聚结直到实现双极性。此外，我们已经确定了关键的蛋白质， 事件在这一途径，揭示这种形式的纺锤体组装的分子机制。 基于这些发现，拟议工作的目标是：1）加深我们对 无中心体纺锤体的组装和组织，以及2）研究促进形成的机制 和无中心体纺锤极的稳定性。线虫和哺乳动物卵母细胞。这些办法将 使我们能够获得卵母细胞减数分裂的机械理解，这是一种重要但知之甚少的形式， 专门的细胞分裂

Project Summary Organisms that reproduce sexually utilize a specialized cell division program called meiosis to reduce their chromosome number by half to generate haploid gametes. Proper execution of this process is crucial for a successful pregnancy, since errors in meiotic chromosome segregation result in aneuploidy (incorrect chromosome number in the embryos), the leading known cause of miscarriages and birth defects in humans. Meiosis in females is especially error prone and this vulnerability has a profound impact on human health: it is estimated that 10-25% of human embryos are chromosomally abnormal, and the vast majority of these defects arise from problems with the female meiotic cells (called oocytes). However, despite the importance of female meiosis for successful reproduction and human health, surprisingly little is known about the mechanisms that act to ensure accurate chromosome partitioning in oocytes. Oocytes have some special features that necessitate the use of novel cell division mechanisms. Perhaps most significantly, oocytes lack centrosomes, which define and organize the spindle poles in other cell types; therefore, spindles in these cells must assemble using different mechanisms. Using C. elegans as a model, we previously demonstrated that acentrosomal spindle assembly proceeds by 1) nucleation/stabilization of microtubules adjacent to the disassembling nuclear envelope, 2) sorting of microtubules such that their minus ends are positioned at the periphery of the array, 3) organization of these ends into nascent poles, and 4) coalescence of these sites until bipolarity is achieved. Moreover, we have identified proteins required for key events in this pathway, shedding light on the molecular mechanisms underlying this form of spindle assembly. Building on these discoveries, the goals of the proposed work are to: 1) deepen our understanding of acentrosomal spindle assembly and organization, and 2) investigate mechanisms that promote the formation and stability of acentrosomal spindle poles in both C. elegans and mammalian oocytes. These approaches will enable us to gain a mechanistic understanding of oocyte meiosis, an important yet poorly understood form of specialized cell division.