Max Planck Institute of Biochemistry, Cell Dynamics Group, Am Klopferspitz 18, D-82152 Martinsried, Germany.
J Cell Sci. 2022 Apr 1;135(7). doi: 10.1242/jcs.259648. Epub 2022 Apr 14.
In multi-nucleate cells of Dictyostelium, cytokinesis is performed by unilateral cleavage furrows that ingress the large cells from their border. We use a septase (sepA)-null mutant with delayed cytokinesis to show that in anaphase a pattern is generated in the cell cortex of cortexillin and myosin II. In multi-nucleate cells, these proteins decorate the entire cell cortex except circular zones around the centrosomes. Unilateral cleavage furrows are initiated at spaces free of microtubule asters and invade the cells along trails of cortexillin and myosin II accumulation. Where these areas widen, the cleavage furrow may branch or expand. When two furrows meet, they fuse, thus separating portions of the multi-nucleate cell from each other. Unilateral furrows are distinguished from the contractile ring of a normal furrow by their expansion rather than constriction. This is particularly evident for expanding ring-shaped furrows that are formed in the centre of a large multi-nucleate cell. Our data suggest that the myosin II-enriched area in multi-nucleate cells is a contractile sheet that pulls on the unilateral furrows and, in that way, expands them.
在粘菌的多核细胞中，胞质分裂是通过从边缘向大细胞内切入的单侧分裂沟来完成的。我们使用了一个有丝分裂后期分离酶（sepA）缺失突变体，其胞质分裂延迟，结果表明在有丝分裂后期，皮层蛋白和肌球蛋白 II 在细胞皮层中形成了一种模式。在多核细胞中，这些蛋白质除了围绕着中心体的圆形区域外，还会修饰整个细胞皮层。单侧分裂沟是从没有微管星状体的空间开始启动的，并沿着皮层蛋白和肌球蛋白 II 积累的轨迹侵入细胞。在这些区域变宽的地方，分裂沟可能会分支或扩张。当两个分裂沟相遇时，它们会融合，从而将多核细胞的不同部分彼此分离。与正常的收缩环相比，单侧分裂沟的特征是扩张而不是收缩。对于在大的多核细胞中心形成的扩展的环形分裂沟，这一点尤为明显。我们的数据表明，多核细胞中的肌球蛋白 II 富集区是一个收缩片，它拉动单侧分裂沟，并以这种方式使其扩张。
