During interphase of the eukaryotic cell cycle, the microtubule (MT) cytoskeleton serves as both a supportive scaffold for organelles and an arborized system of tracks for intracellular transport. At the onset of mitosis, the position of the astral MT network, specifically its center, determines the eventual location of the spindle apparatus and ultimately the cytokinetic furrow. Positioning of the MT aster often results in its movement to the center of a cell, even in large blastomeres hundreds of microns in diameter. This translocation requires positioning forces, yet how these forces are generated and then integrated within cells of varied sizes and geometries remains an open question. Here we describe a method that combines microfluidics, hydrogels, and Xenopus laevis egg extract to investigate the mechanics of aster movement and centration. We determined that asters were able to find the center of artificial channels and annular cylinders, even when cytoplasmic dynein-dependent pulling mechanisms were inhibited. Characterization of aster movement away from V-shaped hydrogel barriers provided additional evidence for a MT-based pushing mechanism. Importantly, the distance over which this mechanism seemed to operate was longer than that predicted by radial aster growth models, agreeing with recent models of a more complex MT network architecture within the aster.

在真核细胞周期的中间阶段，微管（MT）的细胞骨架既是细胞器的支撑支架，又是细胞内运输的轨道状系统。在有丝分裂开始时，星形MT网络的位置，特别是其中心，决定了纺锤体的最终位置，并最终确定了细胞动力学沟。MT aster的定位通常会导致其移动到细胞中心，即使是直径数百微米的大型卵裂球也是如此。这种移位需要定位力，但是如何生成这些力然后将其整合到大小和几何形状不同的单元中仍然是一个悬而未决的问题。在这里，我们描述了一种结合微流体，水凝胶和非洲爪蟾的方法卵提取物以研究紫运动和定心的机理。我们确定，即使抑制了细胞质动力蛋白依赖性的拉动机制，紫苑都能找到人工通道和环形圆柱体的中心。翠菊运动远离V形水凝胶壁垒的特征为基于MT的推动机制提供了更多证据。重要的是，该机制似乎起作用的距离比放射状紫aster增长模型预测的要长，这与紫within内更复杂的MT网络架构的最新模型一致。