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

描述（由申请人提供）：本研究的主要目标是了解控制非肌肉细胞中肌动球蛋白收缩性的基本原理，以秀丽隐杆线虫为模型系统。与骨骼肌收缩不同，在骨骼肌收缩中，力是由肌动蛋白细丝和肌凝蛋白马达稳定的近乎结晶的阵列产生的，而非肌肉细胞的收缩性是马达和细丝之间分布的局部相互作用的结果，这些相互作用会迅速组装、移动和拆卸。了解有组织的细胞尺度收缩行为是如何从这些局部相互作用中产生的，以及个体参与者的局部调节如何“调谐”同一系统以产生不同的行为，对于理解细胞在正常发育和生理过程中如何调节收缩性以及在疾病中如何失调是至关重要的。我们将在一种基本且广泛使用的收缩性模式（称为焦点收缩性）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、收缩和拆卸驱动细胞表面的短暂变形，这些变形被纠正以产生细胞形状变化、皮质流动和组织变形。秀丽隐杆线虫胚胎为研究单个大细胞表面的焦点收缩性提供了一个独特的、易于处理的机会，使用了发达的分子遗传操作、转基因和高分辨率定量光学显微镜工具。我们将使用定量成像、实验操作和预测计算机模拟紧密结合的方法来提出以下问题：1)焦点收缩周期是如何工作的？也就是说，是什么决定局灶性宫缩的开始和结束？2)如何通过调节局部肌凝蛋白活性来调节局灶性收缩，以及肌凝蛋白和肌动蛋白丝组装和拆卸的局部动力学？3)基于我们对肌动蛋白丝、肌凝蛋白、交联剂及其关键调节因子的性质和相互作用的了解，详细的计算机模拟能否再现焦性收缩及其调控的宏观动力学并揭示其基本原理？鉴于参与肌动球蛋白收缩性的分子参与者的广泛保守性，我们的工作将与理解许多其他情况下的收缩性直接相关，无论是在健康还是疾病方面。

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. PUBLIC HEALTH RELEVANCE: The work proposed here aims to elucidate fundamental principles underlying the organization and regulation of actomyosin contractility in non-muscle cells, using C. elegans as a model system. Actomyosin contractility is fundamental to normal development and physiology and is at the heart of processes that underlie birth defects (eg: neurulation) and that go awry in disease (e.g. cell motility in cancer). Because the basic machinery that governs contractility is highly conserved, the results of this work should have direct implications for the understanding of these aberrant states.