Molecular mechanisms of cell shape change in cytokinesis

细胞质分裂，即一个细胞分裂成两个细胞的物理过程，是通过瞬间的 细胞器称为收缩环。PI主要集中在分子和生物物理方面 收缩环功能的机制。PI的实验室正在进行的工作已经产生了一个 对后生动物普遍存在的不对称(非同心)环闭合现象的解释。至 为了解释这种不对称性，提出了一个生物力学反馈回路，在细胞骨架之间 灯丝对齐、灯丝滑动和膜曲率。一种基于此的In Silico模型 反馈可以概括闭合的不对称性，以及闭合启动的动力学 以及线虫受精卵的持续时间，这是这项工作的主要动物模型。 为了扩展和加强这一模型，拟议的工作旨在定义分子和 反馈回路每个组件的物理机制。具体地说，保守的 有助于细胞骨架细丝彼此以及与细胞骨架细丝排列的蛋白质 膜将被定义。肌球蛋白以双极细丝形式存在于 将定义收缩环。最后，在细胞质分裂过程中，细胞的形状将是 描述并与当地蛋白质的丰富和组织相关。 该提案的核心是使用三维活细胞(延时)显微镜和 定量图像分析。几种新的收缩环装配的定量分析方法， 将使用组织和职能。这些方法包括测量F-肌动蛋白排列的方法， 在整个胞质分裂过程中，环关闭的动力学和位置，分子的数量 大分子皮质复合体，以及细胞的三维形状 当然是分组表决。线虫受精卵是这些研究的理想模式系统 由于其可复制的大小、形状和细胞分裂事件的动力学，因此易于彻底 必需蛋白质的耗尽，检查第一次尝试的细胞分裂的能力 蛋白质耗竭，以及稳定表达荧光融合蛋白的菌株的可用性 作为各种亚细胞成分和隔间的标记。重要的是，细胞周期 调控和结构蛋白在线虫和哺乳动物中是保守的。 这项工作的长期目标是帮助抗癌化疗药物的发展 这会阻碍细胞质分裂。靶向作用于收缩环的蛋白质应避免 许多流行药物对非分裂细胞的副作用。此外，由于目前使用的 抗有丝分裂药对某些肿瘤类型的疗效也有限，发展为胞质分裂 药物将是我们对抗癌症的武器库的一个受欢迎的扩展和多样化。

Cytokinesis, the physical division of one cell into two, is accomplished by a transient organelle called the contractile ring. The PI is focused on the molecular and biophysical mechanisms of contractile ring function. Ongoing work in the PI's laboratory has yielded an explanation of asymmetric (non-concentric) ring closure, which is seen throughout metazoa. To explain this asymmetry, a biomechanical feedback loop was proposed, among cytoskeletal filament alignment, filament sliding, and membrane curvature. An in silico model based on this feedback can recapitulate ring closure asymmetry, as well as the kinetics of closure initiation and duration in the C. elegans zygote, the primary animal model for this work. To expand and strengthen this model, the proposed work aims to define the molecular and physical mechanisms of each component of the feedback loop. Specifically, the conserved proteins that contribute to alignment of cytoskeletal filaments with each other and with the membrane will be defined. The existence of myosin in the form of bipolar minifilaments in the contractile ring will be defined. Last, the shape of the cell throughout cytokinesis will be described and correlated with local protein enrichment and organization. The proposal centers on the use of three dimensional live-cell (time-lapse) microscopy and quantitative image analysis. Several novel quantitative assays for contractile ring assembly, organization and function will be used. These include ways to measure F-actin alignment, kinetics and position of ring closure throughout cytokinesis, the number of molecules in macromolecular cortical complexes, and the three-dimensional shape of the cell during the course of division. The C. elegans zygote serves as an ideal model system for these studies due to its reproducible size, shape, and the kinetics of cell division events, the ease of thorough depletion of essential proteins, the ability to examine the first cell division attempted following protein depletion, and the availability of strains stably expressing fluorescent fusion proteins that serve as markers for various subcellular components and compartments. Importantly, cell cycle regulatory and structural proteins are conserved among C. elegans and mammals. The long-term goal of this work is to aid the development of anti-cancer chemotherapeutics that block cytokinesis. Targeting proteins that act specifically in the contractile ring should avoid the side effects on non-dividing cells of many popular drugs. In addition, because currently used anti-mitotics also have limited success against some tumor types, development of cytokinesis drugs will be a welcome expansion and diversification of our arsenal against cancers.