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.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM098441-05
Application #
8895986
Study Section
Nuclear and Cytoplasmic Structure/Function and Dynamics Study Section (NCSD)
Program Officer
Gindhart, Joseph G
Project Start
2011-09-20
Project End
2016-07-31
Budget Start
2015-08-01
Budget End
2016-07-31
Support Year
5
Fiscal Year
2015
Total Cost
$292,314
Indirect Cost
$102,314
Name
University of Chicago
Department
Genetics
Type
Schools of Medicine
DUNS #
005421136
City
Chicago
State
IL
Country
United States
Zip Code
60637
Wu, Youjun; Han, Bingjie; Li, Younan et al. (2018) Rapid diffusion-state switching underlies stable cytoplasmic gradients in the Caenorhabditis elegans zygote. Proc Natl Acad Sci U S A 115:E8440-E8449
McFadden, William M; McCall, Patrick M; Gardel, Margaret L et al. (2017) Filament turnover tunes both force generation and dissipation to control long-range flows in a model actomyosin cortex. PLoS Comput Biol 13:e1005811
Lang, Charles F; Munro, Edwin (2017) The PAR proteins: from molecular circuits to dynamic self-stabilizing cell polarity. Development 144:3405-3416
Stam, Samantha; Alberts, Jon; Gardel, Margaret L et al. (2015) Isoforms Confer Characteristic Force Generation and Mechanosensation by Myosin II Filaments. Biophys J 108:1997-2006
Sailer, Anne; Anneken, Alexander; Li, Younan et al. (2015) Dynamic Opposition of Clustered Proteins Stabilizes Cortical Polarity in the C. elegans Zygote. Dev Cell 35:131-42
Kim, Taeyoon; Gardel, Margaret L; Munro, Ed (2014) Determinants of fluidlike behavior and effective viscosity in cross-linked actin networks. Biophys J 106:526-34
Robin, François B; McFadden, William M; Yao, Baixue et al. (2014) Single-molecule analysis of cell surface dynamics in Caenorhabditis elegans embryos. Nat Methods 11:677-82