Carvalho Ana, Desai Arshad, Oegema Karen
Ludwig Institute for Cancer Research, Department of Cellular and Molecular Medicine, University of California, San Diego, CMM-East 3080, 9500 Gilman Drive, La Jolla, CA 92093, USA.
Cell. 2009 May 29;137(5):926-37. doi: 10.1016/j.cell.2009.03.021.
Cytokinesis is accomplished by constriction of a cortical contractile ring. We show that during the early embryonic divisions in C. elegans, ring constriction occurs in two phases--an initial phase at a constant rate followed by a second phase during which the constriction rate decreases in proportion to ring perimeter. Cytokinesis completes in the same amount of time, despite the reduction in cell size during successive divisions, due to a strict proportionality between initial ring size and the constant constriction rate. During closure, the myosin motor in the ring decreases in proportion to perimeter without turning over. We propose a "contractile unit" model to explain how the ring retains a structural memory of its initial size as it disassembles. The scalability of constriction may facilitate coordination of mitotic events and cytokinesis when cell size, and hence the distance traversed by the ring, varies during embryogenesis and in other contexts.
胞质分裂通过皮质收缩环的收缩来完成。我们发现，在秀丽隐杆线虫的早期胚胎分裂过程中，环收缩分为两个阶段——初始阶段以恒定速率进行，随后是第二阶段，在此阶段收缩速率与环周长成比例下降。尽管在连续分裂过程中细胞大小减小，但由于初始环大小与恒定收缩速率之间存在严格的比例关系，胞质分裂在相同的时间内完成。在收缩过程中，环中的肌球蛋白马达与周长成比例减少，且不会更新。我们提出了一个“收缩单位”模型来解释环在解体时如何保留其初始大小的结构记忆。当细胞大小以及环所经过的距离在胚胎发育和其他情况下发生变化时，收缩的可扩展性可能有助于有丝分裂事件和胞质分裂的协调。
