Department of Physics, Technion- Israel Institute of Technology, Haifa, Israel.
Department of Mathematics, University College London, London, United Kingdom.
Elife. 2020 Apr 21;9:e55368. doi: 10.7554/eLife.55368.
Centering and decentering of cellular components is essential for internal organization of cells and their ability to perform basic cellular functions such as division and motility. How cells achieve proper localization of their organelles is still not well-understood, especially in large cells such as oocytes. Here, we study actin-based positioning mechanisms in artificial cells with persistently contracting actomyosin networks, generated by encapsulating cytoplasmic egg extracts into cell-sized 'water-in-oil' droplets. We observe size-dependent localization of the contraction center, with a symmetric configuration in larger cells and a polar one in smaller cells. Centering is achieved via a hydrodynamic mechanism based on Darcy friction between the contracting network and the surrounding cytoplasm. During symmetry breaking, transient attachments to the cell boundary drive the contraction center to a polar location. The centering mechanism is cell-cycle dependent and weakens considerably during interphase. Our findings demonstrate a robust, yet tunable, mechanism for subcellular localization.
细胞成分的定位和去定位对于细胞的内部组织及其执行基本细胞功能（如分裂和运动）的能力至关重要。细胞如何实现细胞器的正确定位仍未被很好地理解，尤其是在卵母细胞等大型细胞中。在这里，我们通过将细胞质卵提取物包封到细胞大小的“水包油”液滴中，在具有持续收缩肌动球蛋白网络的人工细胞中研究基于肌动蛋白的定位机制。我们观察到收缩中心的大小依赖性定位，在较大的细胞中呈对称构型，在较小的细胞中呈极性构型。定位是通过收缩网络与周围细胞质之间基于达西摩擦力的流体动力机制实现的。在对称性破坏过程中，短暂的细胞边界附着会将收缩中心驱动到一个极性位置。定位机制与细胞周期有关，在间期中会大大减弱。我们的研究结果表明，这是一种强大且可调的亚细胞定位机制。
