Bouvrais Hélène, Chesneau Laurent, Le Cunff Yann, Fairbrass Danielle, Soler Nina, Pastezeur Sylvain, Pécot Thierry, Kervrann Charles, Pécréaux Jacques
CNRS, IGDR - UMR 6290, University of Rennes, Rennes, France.
INRIA, Centre Rennes - Bretagne Atlantique, Rennes, France.
EMBO Rep. 2021 May 5;22(5):e50770. doi: 10.15252/embr.202050770. Epub 2021 Apr 26.
In Caenorhabditis elegans zygote, astral microtubules generate forces essential to position the mitotic spindle, by pushing against and pulling from the cortex. Measuring microtubule dynamics there, we revealed the presence of two populations, corresponding to pulling and pushing events. It offers a unique opportunity to study, under physiological conditions, the variations of both spindle-positioning forces along space and time. We propose a threefold control of pulling force, by polarity, spindle position and mitotic progression. We showed that the sole anteroposterior asymmetry in dynein on-rate, encoding pulling force imbalance, is sufficient to cause posterior spindle displacement. The positional regulation, reflecting the number of microtubule contacts in the posterior-most region, reinforces this imbalance only in late anaphase. Furthermore, we exhibited the first direct proof that dynein processivity increases along mitosis. It reflects the temporal control of pulling forces, which strengthens at anaphase onset following mitotic progression and independently from chromatid separation. In contrast, the pushing force remains constant and symmetric and contributes to maintaining the spindle at the cell centre during metaphase.
在秀丽隐杆线虫受精卵中，星体微管通过向皮层施加推力和拉力，产生对有丝分裂纺锤体定位至关重要的力。我们在那里测量微管动力学时，发现了两种微管群体，分别对应于拉力和推力事件。这提供了一个独特的机会，可在生理条件下研究纺锤体定位力在空间和时间上的变化。我们提出了对拉力的三重控制，分别由极性、纺锤体位置和有丝分裂进程控制。我们表明，动力蛋白结合速率中仅前后不对称，编码拉力不平衡，就足以导致纺锤体向后位移。位置调节反映了最靠后区域微管接触的数量，仅在后期强化这种不平衡。此外，我们展示了第一个直接证据，即动力蛋白的持续运动性在有丝分裂过程中增加。这反映了对拉力的时间控制，在有丝分裂进程后后期开始时增强，且与染色单体分离无关。相比之下，推力保持恒定且对称，并在中期有助于将纺锤体维持在细胞中心。
