Spindle Positioning in Mouse Oocytes Relies on a Dynamic Meshwork of Actin Filaments
Spindle Positioning in Mouse Oocytes Relies on a Dynamic Meshwork of Actin Filaments
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DOI：
10.1016/j.cub.2008.08.044
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发表时间：
2008-10-14
期刊：
影响因子：
9.2
通讯作者：
Verlhac, Marie-Helene
中科院分区：
文献类型：
--
作者：
Azoury, Jessica;Lee, Karen W.;Verlhac, Marie-Helene
高等生物体中的雌性减数分裂由高度不对称的分裂组成，其将大部分母体储存保留在卵母细胞中用于胚胎发育。细胞质的不对称分配是由纺锤体的“偏离中心”定位造成的，在小鼠卵母细胞中，这主要取决于肌动蛋白丝 [1, 2]。与大多数系统相比，这是一种独特的情况，其中纺锤体定位需要星体微管和皮质肌动蛋白丝之间的相互作用[3]。 Formin 2 是一种直肌动蛋白丝成核剂，是小鼠卵母细胞第一次减数分裂纺锤体迁移至皮质和胞质分裂所必需的 [4,5]。尽管在该模型中已经很好地确定了肌动蛋白丝控制纺锤体定位的要求，但没有人能够在细胞质中检测到它们[6]。通过 F-肌动蛋白特异性探针的表达和实时共聚焦显微镜，我们展示了由 Formin 2 组织的细胞质肌动蛋白网络的存在，该网络控制着纺锤体的迁移。在减数分裂 1 晚期，这些丝组织成纺锤状 F-肌动蛋白结构，与皮质相连。在后期，该网络的全局重组允许极体挤出。此外，使用肌动蛋白-YFP，我们的 FRAP 分析证实了高度动态的细胞质肌动蛋白网络的存在，该网络在时间和空间上受到严格调控。
Female meiosis in higher organisms consists of highly asymmetric divisions, which retain most maternal stores in the oocyte for embryo development. Asymmetric partitioning of the cytoplasm results from the spindle's "off-center" positioning, which, in mouse oocytes, depends mainly on actin filaments [1, 2]. This is a unique situation compared to most systems, in which spindle positioning requires interactions between astral microtubules and cortical actin filaments [3]. Formin 2, a straight-actin-filament nucleator, is required for the first meiotic spindle migration to the cortex and cytokinesis in mouse oocytes [4,5]. Although the requirement for actin filaments in the control of spindle positioning is well established in this model, no one has been able to detect them in the cytoplasm [6]. Through the expression of an F-actin-specific probe and live confocal microscopy, we show the presence of a cytoplasmic actin meshwork, organized by Formin 2, that controls spindle migration. In late meiosis 1, these filaments organize into a spindle-like F-actin structure, which is connected to the cortex. At anaphase, global reorganization of this meshwork allows polar-body extrusion. In addition, using actin-YFP, our FRAP analysis confirms the presence of a highly dynamic cytoplasmic actin meshwork that is tightly regulated in time and space.