推动细胞形状发生变化的力

　　推动细胞形状发生变化的力在发育中起根本性作用。在有丝分裂过程中，粘附细胞从扁平形变成圆形，这种变化被认为是细胞分裂的几何要求所必需的。Stewart等人研究了推动这种形状变化的力。他们发现，有丝分裂中让细胞形状变成圆形的力既取决于肌动球蛋白的细胞骨架，又取决于细胞调控“克分子渗透压浓度”的能力。让细胞形状变成圆形的力是由渗透压产生的，肌动球蛋白皮质通过抵抗外力来维持这种变圆的力。这些结果支持以下观点：在动物细胞中，肌动球蛋白皮质起细胞内壁的作用，引导渗透扩张来控制细胞形状。

　　推荐原文出处：

　　Nature  doi:10.1038/nature09642

　　Hydrostatic pressure and the actomyosin cortex drive mitotic cell rounding

　　Martin P. Stewart,Jonne Helenius,Yusuke Toyoda,Subramanian P. Ramanathan,Daniel J. Muller& Anthony A. Hyman

　　During mitosis, adherent animal cells undergo a drastic shape change, from essentially flat to round1, 2, 3. Mitotic cell rounding is thought to facilitate organization within the mitotic cell and be necessary for the geometric requirements of division4, 5, 6, 7. However, the forces that drive this shape change remain poorly understood in the presence of external impediments, such as a tissue environment2. Here we use cantilevers to track cell rounding force and volume. We show that cells have an outward rounding force, which increases as cells enter mitosis. We find that this mitotic rounding force depends both on the actomyosin cytoskeleton and the cells’ ability to regulate osmolarity. The rounding force itself is generated by an osmotic pressure. However, the actomyosin cortex is required to maintain this rounding force against external impediments. Instantaneous disruption of the actomyosin cortex leads to volume increase, and stimulation of actomyosin contraction leads to volume decrease. These results show that in cells, osmotic pressure is balanced by inwardly directed actomyosin cortex contraction. Thus, by locally modulating actomyosin-cortex-dependent surface tension and globally regulating osmotic pressure, cells can control their volume, shape and mechanical properties.