Bringmann Henrik
Max Planck Institute for Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany.
Biochem Soc Trans. 2008 Jun;36(Pt 3):381-3. doi: 10.1042/BST0360381.
The mitotic spindle positions the cytokinesis furrow. The cytokinesis furrow then forms and ingresses at the site of the mitotic spindle, between the spindle poles. Two populations of spindle microtubules are implicated in cytokinesis furrow positioning: radial microtubule arrays called asters and bundled non-kinetochore microtubules called the spindle midzone. Here I will discuss our recent results that provided examples of how aster-positioned and midzone-positioned cytokinesis can be mechanically and genetically separated. These experiments illustrate how asters and midzone contribute to cytokinesis. ASS (asymmetric spindle severing) is a mechanical way to spatially separate the aster and midzone signals. In Caenorhabditis elegans embryos, asters and midzone provide two consecutive signals that position the cytokinesis furrow. The first signal is positioned midway between the microtubule asters; the second signal is positioned over the spindle midzone. Aster and midzone contribution can also be genetically separated. Mutants in spd-1 have no detectable midzone and are defective in midzone-positioned but not aster-positioned cytokinesis. Disruption of the function of LET-99 and the heterotrimeric G-proteins GOA-1/GPA-16 and their regulator GPR-1/2 causes defects in aster-positioned cytokinesis but not in midzone-positioned cytokinesis. In order to understand aster-positioned cytokinesis we have to understand how microtubule asters spatially control the activity of LET-99, GPR-1/2 and GOA-1/GPA-16 and how the activity of these G-protein pathway components control the assembly of a contractile ring.
有丝分裂纺锤体确定胞质分裂沟的位置。随后，胞质分裂沟在有丝分裂纺锤体的位置形成并向内凹陷，位于纺锤体两极之间。两类纺锤体微管参与胞质分裂沟的定位：一类是称为星状体的径向微管阵列，另一类是成束的非动粒微管，即纺锤体中间区。在此，我将讨论我们最近的研究结果，这些结果提供了星状体定位和中间区定位的胞质分裂如何在机械和遗传层面上被分离的实例。这些实验说明了星状体和中间区在胞质分裂中所起的作用。不对称纺锤体切断（ASS）是一种在空间上分离星状体和中间区信号的机械方法。在秀丽隐杆线虫胚胎中，星状体和中间区提供了两个连续的信号来确定胞质分裂沟的位置。第一个信号位于微管星状体之间的中间位置；第二个信号位于纺锤体中间区上方。星状体和中间区的作用也可以在遗传层面上被分离。spd - 1基因的突变体没有可检测到的中间区，在中间区定位的胞质分裂中存在缺陷，但在星状体定位的胞质分裂中没有缺陷。LET - 99以及异源三聚体G蛋白GOA - 1/GPA - 16及其调节因子GPR - 1/2的功能破坏会导致星状体定位的胞质分裂出现缺陷，但不会导致中间区定位的胞质分裂出现缺陷。为了理解星状体定位的胞质分裂，我们必须了解微管星状体如何在空间上控制LET - 99、GPR - 1/2和GOA - 1/GPA - 16的活性，以及这些G蛋白信号通路组分的活性如何控制收缩环的组装。
