Modeling mitotic spindle assembly

描述(申请人提供)：有丝分裂纺锤体是一种复杂的分子机器，在细胞分裂前分离染色体。一个多世纪以来，它一直是基础生物学研究的热点，此外，它还是最重要的医学细胞结构之一，因为它的故障会导致出生缺陷、癌症和死亡。虽然分子清单和主轴机械的一般原理正在变得清晰，但对主轴的系统生物学缺乏详细的了解。我们的长期目标是在系统水平上定量了解有丝分裂纺锤体的机械化学。这种理解必须分阶段实现，首先回答更简单的问题，然后回答更困难的问题，例如：不同结构的微管群体如何相互作用，以确保快速和准确的纺锤体组装？如何整合多个分子马达和微管动力学来确定复杂形状细胞中纺锤体结构的精确纺锤体长度和空间位置？肌动蛋白、肌球蛋白和膜动力学是否影响纺锤体的发育？我们将通过数学分析、计算机模拟和模型驱动实验的新组合来回答这些问题，以检验一般假设，即运动、微管和肌动球蛋白产生的力的作用与微管动力学相结合，可以快速准确地组装纺锤体，确定其长度，并将其放置在细胞中。我们根据观察和建模估计得出以下结论：(I)在许多细胞中，中心体微管和染色体微管都有助于纺锤体的组装；(Ii)动力蛋白马达牵引力、肌动蛋白收缩和微管动力学有助于微管位于细胞中心的位置；(Iii)在果蝇合胞体中，动蛋白、动力蛋白和肌动球蛋白的力和运输调节有丝分裂纺锤体和沟槽的长度。基于这些结果，具体目的是：1.验证中心体和染色体微管动力学及时整合和协调的假设，以实现快速而准确的有丝分裂纺锤体组装。2.验证动力蛋白拉力、肌动蛋白收缩和微管推力三种力的平衡对微管定位的影响这一假设。3.检验内在动力和外在动力蛋白、微管和肌球蛋白力以及运动运输的平衡假设，决定合胞果蝇有丝分裂纺锤体和沟槽的长度和位置。所提出的理论和实验工作将导致(I)有丝分裂纺锤体结构的电子重组，(Ii)定量了解多个聚合物/马达的力平衡和动力学如何调节有丝分裂纺锤体的组装、大小和定位，以及(Iii)开发适用于各种细胞力学问题的新的建模框架。项目简介：对有丝分裂机制的更好了解将导致更有效地开发新的治疗方法来治疗与有丝分裂缺陷相关的功能障碍，如与出生缺陷和癌症相关的非整倍体。该建模框架将适用于一些基本的机械力化学过程，例如 细胞质分裂和细胞运动，对它们的定量了解对于生物医学应用是很重要的。

DESCRIPTION (provided by applicant): Mitotic spindle is a complex molecular machine segregating chromosomes before cell division. It has been of great interest for fundamental biological research for more than a century, in addition to being one of the most medically important cell structures, as its malfunction leads to birth defects, cancer and death. While molecular inventory and general principles of the spindle mechanics are becoming clear, detailed understanding of the spindle's systems biology is lacking. Our long-term goal is systems-level quantitative understanding of mitotic spindle's mechanochemistry. This understanding has to be achieved in stages, first answering simpler, and then more difficult questions, such as: How do structurally different microtubule populations interact to ensure rapid and accurate spindle assembly? How are multiple molecular motors and microtubule dynamics integrated to determine precise spindle length and spatial positioning of the spindle structures in complex-shaped cells? Do actin, myosin and membrane dynamics affect spindle development? We will answer these questions by using a novel combination of mathematical analysis, computer simulations and model-driven experiments to test the general hypothesis that actions of motor-, microtubule-, and actomyosin-generated forces combine with microtubule dynamics to rapidly and accurately assemble the spindle, determine its length, and position it in the cell. We base this hypothesis on the observations and modeling estimates suggesting that: (i) In many cells, both centrosomal and chromosomal microtubules contribute to spindle assembly; (ii) Dynein motor pulling forces, actomyosin contraction, and microtubule dynamics contribute to microtubule asters' positioning at the cell center; (iii) Kinesin, dynein and actomyosin forces and transport regulate mitotic spindle and furrow lengths in Drosophila syncytium. Based on these results, the specific aims are to: 1. Test the hypothesis that centrosomal and chromosomal microtubule dynamics are integrated and coordinated in time to achieve rapid and accurate mitotic spindle assembly. 2. Test the hypothesis that balance of three forces - dynein pulling, actomyosin contraction, and microtubule pushing - is responsible for positioning of microtubule asters. 3. Test the hypothesis that balance of intrinsic kinesin forces and extrinsic dynein, microtubule and actomyosin forces, and motor transport, determine lengths and positions of the mitotic spindle and furrow in Drosophila syncytium. The proposed theoretical and experimental work will result in (i) in silico reconstitution of the mitotic spindle structures, (ii) quantitative understanding how multiple polymer/motor force balance and dynamics regulate mitotic spindle assembly, size and positioning, and (iii) development of a novel modeling framework applicable to a broad variety of cell mechanical problems. Project Narrative: An improved understanding of mitotic mechanisms will lead to more effective development of new therapies for treatment of mitosis defect-related dysfunctions such as aneuploidy associated with birth defects and cancer. The modeling framework will be applicable for a number of fundamental mechanochemical processes such as cytokinesis and cell motility, a quantitative understanding of which is important for biomedical applications.