The spindle shows remarkable diversity, and changes in an integrated fashion, as cells vary over evolution. Here, we provide a mechanistic explanation for variations in the first mitotic spindle in nematodes. We used a combination of quantitative genetics and biophysics to rule out broad classes of models of the regulation of spindle length and dynamics, and to establish the importance of a balance of cortical pulling forces acting in different directions. These experiments led us to construct a model of cortical pulling forces in which the stoichiometric interactions of microtubules and force generators (each force generator can bind only one microtubule), is key to explaining the dynamics of spindle positioning and elongation, and spindle final length and scaling with cell size. This model accounts for variations in all the spindle traits we studied here, both within species and across nematode species spanning over 100 million years of evolution.

中文翻译：

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化学计量相互作用解释了 1 亿年线虫进化过程中的纺锤体动力学和缩放比例

随着细胞在进化过程中发生变化，纺锤体显示出显着的多样性，并以综合方式发生变化。在这里，我们为线虫中第一个有丝分裂纺锤体的变化提供了机械解释。我们结合使用数量遗传学和生物物理学来排除各种调节纺锤体长度和动力学的模型，并确定作用于不同方向的皮层拉力平衡的重要性。这些实验使我们构建了一个皮质拉力模型，其中微管和力发生器的化学计量相互作用（每个力发生器只能结合一个微管）是解释纺锤体定位和伸长动力学的关键，以及纺锤体最终长度和随细胞大小缩放。