Modeling mitotic spindle assembly

描述（由申请人提供）：有丝分裂纺锤体是细胞分裂前分离染色体的复杂分子机器。世纪以来，除了作为医学上最重要的细胞结构之一之外，它还对基础生物学研究产生了极大的兴趣，因为它的故障导致出生缺陷，癌症和死亡。虽然分子库存和纺锤体力学的一般原则正在变得清晰，但缺乏对纺锤体系统生物学的详细了解。我们的长期目标是系统水平的定量理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，然后是更困难的问题，例如：结构不同的微管群体如何相互作用以确保快速准确的纺锤体组装？如何整合多个分子马达和微管动力学，以确定复杂形状细胞中纺锤体结构的精确长度和空间定位？肌动蛋白、肌球蛋白和膜动力学影响纺锤体发育吗？我们将回答这些问题，通过使用一种新的组合的数学分析，计算机模拟和模型驱动的实验来测试一般的假设，即电机，微管和肌动球蛋白产生的力量联合收割机结合微管动力学，以快速，准确地组装纺锤体，确定其长度，并将其定位在细胞中的行动。我们基于以下观察和模型估计提出这一假设：（i）在许多细胞中，中心体和染色体微管都有助于纺锤体组装;（ii）动力蛋白马达拉力、肌动球蛋白收缩和微管动力学有助于微管星状体在细胞中心的定位;（iii）驱动蛋白、动力蛋白和肌动球蛋白的力和运输调节果蝇合胞体中有丝分裂纺锤体和沟的长度。根据这些结果，具体目标是：1。验证中心体和染色体微管动力学在时间上是整合和协调的，以实现快速和准确的有丝分裂纺锤体组装的假设。2.测试以下假设：动力蛋白拉动、肌动球蛋白收缩和微管推动这三种力的平衡负责微管星状体的定位。3.测试的假设，即平衡的内在驱动力和外在动力蛋白，微管和肌动球蛋白的力量，和电机运输，确定的长度和位置的有丝分裂纺锤体和沟在果蝇合胞体。拟议的理论和实验工作将导致（i）在硅片重建的有丝分裂纺锤体结构，（ii）定量了解多个聚合物/电机力平衡和动力学如何调节有丝分裂纺锤体组装，大小和定位，以及（iii）开发一种新的建模框架适用于各种各样的细胞力学问题。项目叙述：对有丝分裂机制的更好理解将导致更有效地开发用于治疗有丝分裂缺陷相关功能障碍的新疗法，例如与出生缺陷和癌症相关的非整倍体。建模框架将适用于一些基本的机械化学过程，如 胞质分裂和细胞运动，定量了解这是重要的生物医学应用。

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.