Computational Analysis and Modeling of Contractile Ring Assembly

描述（由申请人提供）：在细胞分裂过程中，肌动蛋白、肌凝蛋白、形成蛋白和相关蛋白自组装成赤道肌动蛋白-肌凝蛋白收缩环。环的收缩将分裂细胞的细胞质分成两部分。虽然分子参与者的名单几乎是完整的，但驱动环组装和收缩的分子和集体机制仍然不清楚。我们将与实验人员合作开发计算工具，用于分析分裂酵母细胞表达肌动蛋白（GFP-CHD）和肌球蛋白（Rlc1p-RFP）荧光标记物的图像，这些荧光标记物揭示了收缩环形成模式的关键信息。然后，我们将使用这些信息来开发和测试收缩环组件的力学和动力学的数学和数值模型，并激励进一步的实验。在裂变酵母菌中，收缩环通过肌动蛋白依赖的缩合，聚集了一宽带的膜结合“节点”，其中包含肌凝蛋白Myo2p， formin Cdc12p和其他蛋白质。缩合机制是高度动态的，包括连续的肌动蛋白聚合和分解以及间歇性的节点运动。Cdc12p可能是肌动蛋白丝的核，肌动蛋白丝在节点之间建立瞬时连接，这些连接通过Myo2p运动活动拉在一起并形成一个环。我们将通过开发新的计算方法来测试这一假设，以在3D静态图像中分割肌动蛋白丝，并在延时电影中跟踪肌动蛋白丝和束。这将使我们能够分析凝聚肌动球蛋白网络的拓扑结构和动力学，并系统地量化顶点的位置、丝的长度、聚合、分解和捆绑的速率。通过将这些动态与Myo2p节点的位置相关联，我们将严格建立节点与肌动蛋白重塑位点之间的关系。成功跟踪肌动蛋白运动将进一步使我们能够提取生物物理参数值，如丝扩散系数，细胞质粘度和力。我们将模拟物理约束在节点之间建立连接的机制中的作用，以及力对formin介导的肌动蛋白延伸的影响。我们将测试环总成的全局模型，并开发统计分析和可视化方法，以便对模型预测进行系统比较。细胞质分裂是细胞分裂的最后一步，是由一个由肌动蛋白和相关蛋白组成的赤道收缩环的收缩驱动的。尽管破译细胞分裂的机制和控制在生物医学上具有重要意义，但收缩环组装和收缩的确切机制步骤仍不清楚。我们将通过分析分裂细胞的荧光显微镜图像和开发数值和数学机制模型来解决可收缩环组装的定量细节。

DESCRIPTION (provided by applicant): During cytokinesis, actin, myosin, formins and associated proteins, self-assemble into the equatorial acto-myosin contractile ring. The constriction of the ring separates the cytoplasm of dividing cells into two. While the list of molecular players is almost complete, the molecular and collective mechanisms driving the assembly and constriction of the ring remain unclear. We will collaborate with experimentalists to develop computational tools for the analysis of images of dividing fission yeast cells expressing fluorescent markers for actin (GFP-CHD) and myosin (Rlc1p-RFP), which reveal crucial information on the pattern of contractile ring formation. We will then use the information to develop and test mathematical and numerical models of the mechanics and dynamics of contractile ring assembly and to motivate further experiments. In fission yeast, the contractile ring assembles through the actin-dependent condensation of a broad band of membrane-bound "nodes" containing myosin Myo2p, formin Cdc12p, and other proteins. The condensation mechanism is highly dynamic involving continuous actin polymerization and disassembly and intermittent node motions. Cdc12p presumably nucleates actin filaments which establish transient connections between nodes that are pulled together and form a ring through Myo2p motor activity. We will test this hypothesis by developing novel computational methods to segment actin filaments in 3D static images and to track actin filaments and bundles in time-lapse movies. This will enable us to analyze the topology and dynamics of condensing actomyosin networks and systematically quantify the locations of vertices, filament lengths, rates of polymerization, disassembly, and bundling. By correlating these dynamics to the locations of Myo2p nodes we will rigorously establish the relationship between nodes and sites of actin remodeling. Successful tracking of actin motions will further allow us to extract biophysical parameter values such as filament diffusion coefficients, cytoplasmic viscosity, and forces. We will model the role of physical constraints on the mechanism of establishing connections between nodes and the effect of force on formin-mediated actin elongation. We will test global models of ring assembly and develop statistical analysis and visualization methods for systematic comparison of model predictions to experiment. Cytokinesis, the final step of cell division, is driven by the constriction of an equatorial contractile ring consisting of actin and associated proteins. Despite the biomedical importance of deciphering the mechanisms and controls of cell division, the precise mechanistic steps of contractile ring assembly and constriction remain unclear. We will resolve quantitative details of the assembly of the contractile ring by analyzing fluorescence microscopy images of dividing cells and by developing numerical and mathematical mechanistic models.