Department of Computational and Systems Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America.
PLoS One. 2012;7(6):e38921. doi: 10.1371/journal.pone.0038921. Epub 2012 Jun 14.
Positioning of the mitotic spindle through the interaction of astral microtubules with the cell boundary often determines whether the cell division will be symmetric or asymmetric. This process plays a crucial role in development. In this paper, a numerical model is presented that deals with the force exerted on the spindle by astral microtubules that are bent by virtue of their confinement within the cell boundary. It is found that depending on parameters, the symmetric position of the spindle can be stable or unstable. Asymmetric stable equilibria also exist, and two or more stable positions can exist simultaneously. The theory poses new types of questions for experimental research. Regarding the cases of symmetric spindle positioning, it is necessary to ask whether the microtubule parameters are controlled by the cell so that the bending mechanics favors symmetry. If they are not, then it is necessary to ask what forces external to the microtubule cytoskeleton counteract the bending effects sufficiently to actively establish symmetry. Conversely, regarding the cases with asymmetry, it is now necessary to investigate whether the cell controls the microtubule parameters so that the bending favors asymmetry apart from any forces that are external to the microtubule cytoskeleton.
有丝分裂纺锤体的定位是通过星体微管与细胞边界的相互作用来实现的，这通常决定了细胞分裂是对称的还是不对称的。这个过程在发育过程中起着至关重要的作用。在本文中，提出了一个数值模型，用于处理由于被细胞边界限制而弯曲的星体微管对纺锤体施加的力。结果表明，根据参数的不同，纺锤体的对称位置可能是稳定的，也可能是不稳定的。也存在不对称的稳定平衡点，并且可以同时存在两个或更多的稳定位置。该理论为实验研究提出了新的问题。对于对称的纺锤体定位的情况，有必要问微管参数是否由细胞控制，以使弯曲力学有利于对称。如果不是，那么就有必要问微管细胞骨架之外的什么力足以抵消弯曲效应，从而主动建立对称性。相反，对于不对称的情况，现在有必要研究细胞是否控制微管参数，以使弯曲有利于不对称，而不管微管细胞骨架之外的任何力如何。
