Dynamics and regulation of actomyosin contractility in the C. elegans embryo

描述(由申请人提供)：这项研究的广泛目标是以秀丽线虫为模型系统，了解控制非肌肉细胞肌动球蛋白收缩的基本原理。与骨骼肌收缩不同，在骨骼肌收缩中，力是由稳定的几乎结晶的肌动蛋白细丝和肌球蛋白马达阵列产生的，非肌肉细胞的收缩能力是马达和肌球蛋白马达之间分布的局部制力相互作用的全球结果，它们在相互作用时迅速组装、移动和分解。理解如何从这些局部相互作用中产生有组织的细胞尺度的收缩行为，以及个体参与者的局部调节如何“调节”相同的系统以产生不同的行为，对于理解细胞如何在正常发育和生理过程中调节收缩能力以及在疾病中如何失调是至关重要的。我们将在一种基本的和广泛使用的收缩模式-称为局灶性收缩-的背景下解决这些挑战，在这种模式中，收缩网络的周期性组装、收缩和拆解驱动细胞表面的瞬时变形，这些变形被矫正以产生细胞形状改变、皮质流动和组织变形。线虫胚胎提供了一个独特的易于处理的机会来研究单个大细胞表面的局部收缩性能，使用成熟的分子遗传操作、转基因和高分辨率定量光学显微镜的工具。我们将使用定量成像、实验操作和预测性计算机模拟的紧密结合来提出以下问题：1)局部收缩循环是如何工作的？2)如何通过调节局部肌球蛋白的活性以及肌球蛋白和肌动蛋白细丝组装和分解的局部动力学来调节局部收缩能力？3)基于我们所知的肌动蛋白细丝、肌球蛋白、交联物及其关键调节因子的性质和相互作用的详细的计算机模拟，能够再现局部收缩的宏观动力学及其调节，并揭示基本的基本原理？鉴于参与肌动球蛋白收缩的分子成员的广泛保守性，我们的工作将与理解许多其他背景下的收缩直接相关，包括在健康和疾病方面。

DESCRIPTION (provided by applicant): The broad goal of this study is to understand the basic principles that govern actomyosin contractility in non-muscle cells, using C. elegans as a model system. Unlike in skeletal muscle contraction, where force is produced by stable almost crystalline arrays of actin filaments and myosin motors, contractility in non-muscle cells is the global consequence of distributed local force-generating interactions among motors and filaments that rapidly assemble, move and dissemble as they interact. Understanding how organized cell-scale contractile behaviors emerge from these local interactions, and how local regulation of the individual players "tunes" the same system to produce different behaviors, is fundamental to understanding how cells regulate contractility during normal development and physiology and how it is dysregulated in disease. We will address these challenges in the context of a fundamental and widely used mode of contractility - called focal contractility - in which the periodic assembly, contraction and disassembly of contractile networks drive transient deformations of the cell surface that are rectified to produce cell shape change, cortical flow and tissue deformation. The C. elegans embryo provides a uniquely tractable opportunity to study focal contractility at the surface of single large cells using well-developed tools for molecular genetic manipulation, transgenesis, and high-resolution quantitative light microscopy. We will use a tightly integrated combination of quantitative imaging, experimental manipulations, and predictive computer simulations to ask the following questions: 1) How does the focal contractility cycle work? i.e. what governs the initiation and termination of focal contractions? 2) How is focal contractility regulated by tuning local myosin activity, and the local kinetics of myosin and actin filament assembly and disassembly? 3) Can detailed computer simulations, based on what we know about the properties of and interactions among actin filaments, myosin, crosslinkers and their key regulators, reproduce the macroscopic dynamics of focal contractility and its regulation and reveal the fundamental underlying principles? Given the extensive conservation of molecular players involved in actomyosin contractility, our work will have direct relevance to understanding contractility in many other contexts, both in health and disease.