Xu Yitong, Chao Anna, Rinaldin Melissa, Kickuth Alison, Brugués Jan, Di Talia Stefano
Department of Cell Biology, Duke University Medical Center, Durham, NC 27705, USA; Duke Center for Quantitative Living Systems, Duke University Medical Center, Durham, NC 27710, USA.
Cluster of Excellence Physics of Life, TU Dresden, Dresden 01307, Germany; Max Planck Institute of Molecular Cell Biology and Genetics, Dresden 01307, Germany; Center of Systems Biology, Dresden 01307, Germany.
Curr Biol. 2025 Feb 3;35(3):655-664.e3. doi: 10.1016/j.cub.2024.11.046. Epub 2025 Jan 9.
Anaphase is tightly controlled spatiotemporally to ensure proper separation of chromosomes. The mitotic spindle, the self-organized microtubule structure driving chromosome segregation, scales in size with the available cytoplasm. Yet, the relationship between spindle size and chromosome movement remains poorly understood. Here, we address this relationship during the cleavage divisions of the Drosophila blastoderm. We show that the speed of chromosome separation gradually decreases during the four nuclear divisions of the blastoderm. This reduction in speed is accompanied by a similar reduction in spindle length, ensuring that these two quantities are tightly linked. Using a combination of genetic and quantitative imaging approaches, we find that two processes contribute to controlling the speed at which chromosomes move in anaphase: the activity of molecular motors important for microtubule depolymerization and sliding and the cell cycle oscillator. Specifically, we found that the levels of multiple kinesin-like proteins important for microtubule depolymerization, as well as kinesin-5, contribute to setting the speed of chromosome separation. This observation is further supported by the scaling of poleward flux rate with the length of the spindle. Perturbations of the cell cycle oscillator using heterozygous mutants of mitotic kinases and phosphatases revealed that the duration of anaphase increases during the blastoderm cycles and is the major regulator of chromosome velocity. Thus, our work suggests a link between the biochemical rate of mitotic exit and the forces exerted by the spindle. Collectively, we propose that the cell cycle oscillator and spindle length set the speed of chromosome separation in anaphase.
后期在时空上受到严格控制，以确保染色体的正确分离。有丝分裂纺锤体是驱动染色体分离的自组织微管结构，其大小与可用细胞质成比例。然而，纺锤体大小与染色体运动之间的关系仍知之甚少。在这里，我们研究果蝇胚盘分裂过程中的这种关系。我们表明，在胚盘的四次核分裂过程中，染色体分离的速度逐渐降低。速度的降低伴随着纺锤体长度的类似降低，确保这两个量紧密相关。通过结合遗传和定量成像方法，我们发现有两个过程有助于控制染色体在后期移动的速度：对微管解聚和滑动重要的分子马达的活性以及细胞周期振荡器。具体来说，我们发现对微管解聚重要的多种类驱动蛋白以及驱动蛋白-5的水平有助于设定染色体分离的速度。极向通量率与纺锤体长度的比例关系进一步支持了这一观察结果。使用有丝分裂激酶和磷酸酶的杂合突变体对细胞周期振荡器进行扰动，结果表明在胚盘周期中，后期的持续时间增加，并且是染色体速度的主要调节因子。因此，我们的工作表明有丝分裂退出的生化速率与纺锤体施加的力之间存在联系。总体而言，我们提出细胞周期振荡器和纺锤体长度设定了后期染色体分离的速度。
