Chromatids segregate without centrosomes during Caenorhabditis elegans mitosis in a Ran- and CLASP-dependent manner.
Chromatids segregate without centrosomes during Caenorhabditis elegans mitosis in a Ran- and CLASP-dependent manner.
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DOI：
10.1091/mbc.e14-12-1577
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发表时间：
2015-06-01
影响因子：
3.3
通讯作者：
Delattre M
中科院分区：
文献类型：
--
作者：
Nahaboo W;Zouak M;Askjaer P;Delattre M
激光消融单细胞秀丽隐杆线虫胚胎中的着丝体表明，在有丝分裂过程中染色单体可以独立于着丝体分离，也可以独立于着丝点微管的活性分离。CLASP和RanGTP需要产生这种与中心体无关的力，而SPD-1和BMK-1则起到刹车的作用来对抗这种力。在有丝分裂期间，染色体连接到基于微管的纺锤体上。目前的模型认为纺锤杆的位移和/或着丝点微管的活动产生分离姐妹染色单体的机械力。利用激光破坏秀丽隐杆线虫有丝分裂过程中的中心体，我们发现这两种机制都不是实现正确染色单体分离所必需的。我们的结果强烈表明，纺锤体中间区产生的向外的力，独立于中心体，足以分离有丝分裂细胞中的染色体。通过突变体和RNAi分析，我们发现微管捆绑蛋白SPD-1/MAP-65和BMK-1/kinesin-5可以抑制纺锤体中部产生的力。相反，我们发现了两种微管生长和成核剂Ran和CLASP在后期建立与中心体无关的力方面的新作用。它们的参与提出了一种有趣的可能性，即在有丝分裂期间，持续需要中间区微管的微管聚合来维持染色体分离。
Laser ablation of centrosomes in one-cell Caenorhabditis elegans embryos shows that chromatids can segregate independently of centrosomes and also independently of the activity of kinetochore microtubules during mitosis. CLASP and RanGTP are required to generate this centrosome-independent force, whereas SPD-1 and BMK-1 act as brakes to oppose it. During mitosis, chromosomes are connected to a microtubule-based spindle. Current models propose that displacement of the spindle poles and/or the activity of kinetochore microtubules generate mechanical forces that segregate sister chromatids. Using laser destruction of the centrosomes during Caenorhabditis elegans mitosis, we show that neither of these mechanisms is necessary to achieve proper chromatid segregation. Our results strongly suggest that an outward force generated by the spindle midzone, independently of centrosomes, is sufficient to segregate chromosomes in mitotic cells. Using mutant and RNAi analysis, we show that the microtubule-bundling protein SPD-1/MAP-65 and BMK-1/kinesin-5 act as a brake opposing the force generated by the spindle midzone. Conversely, we identify a novel role for two microtubule-growth and nucleation agents, Ran and CLASP, in the establishment of the centrosome-independent force during anaphase. Their involvement raises the interesting possibility that microtubule polymerization of midzone microtubules is continuously required to sustain chromosome segregation during mitosis.