The broad goal of this study is to elucidate basic mechanisms by which embryonic cells exert rapid spatiotemporal control over subcellular organization and force production to move, change shape, divide and execute tissue morphogenesis. Cells do this in part by patterning intracellular signals that regulate assembly and force production by the actomyosin cytoskeleton. At same time, cytoskeletal dynamics and contractility feed back to modulate the distributions and activities of their upstream regulators. A fundamental challenge is to understanding how robust spatiotemporal control of cell behavior emerges from dynamic interplay of intracellular signaling, cytoskeletal dynamics and cytomechanics, and how failures in this process produce developmental defects and human disease. We will address this challenge using the C. elegans embryo as a model system to study two fundamental, widespread and highly conserved forms of mechanochemical patterning: The first is pulsed actomyosin contractility in which the episodic assembly, contraction and disassembly of contractile networks drive transient deformations of the cell surface to control cell shape change, cortical flow and tissue deformation. The second is dynamic formation and stabilization of cortical polarity through interactions among conserved PAR polarity proteins, Rho family GTPases and the actomyosin cytoskeleton. C. elegans embryos provide a unique opportunity to study these processes at the surface of single large cells in vivo using quantitative microscopy and well-developed tools for genetic manipulation. Building on our previous studies, we will use a tightly integrated combination of quantitative imaging, experimental manipulations, and predictive computer simulations to address the following questions: 1) How do tunable spatiotemporal dynamics of pulsed contractility emerge from dynamic coupling of RhoA signaling and actomyosin contractility? 2) How are stable boundaries between polarized domains maintained in the face of continuous exchange and diffusion, through dynamic clustering, positive feedback and mutual antagonism of polarity proteins? 3) How is the polarity boundary maintained in the face of persistent contractile asymmetries through feedback mechanisms that couple PAR proteins, small GTPases and actomyosin contractility? Because the molecular players involved in these processes are highly conserved, our work will have direct relevance for understanding cell polarity and spatiotemporal control of actomyosin contractility in many other contexts, both in health and disease.

Public Health Relevance

The work proposed here aims to uncover basic principles and mechanisms that underlie spatiotemporal regulation of actomyosin contractility and cell polarity, using C. elegans as a model system. Dynamic control of actomyosin contractility and cell polarity are essential for normal development and physiology, as well as wound repair, and failures in this control are directly linked to developmental defects, cancer initiation and progression and numerous other diseases. Because the basic machinery that governs cell polarity and actomyosin contractility is highly conserved, the results of this work should have direct implications for understanding their roles in both normal biology and various disease states.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
Project #
Application #
Study Section
Nuclear and Cytoplasmic Structure/Function and Dynamics Study Section (NCSD)
Program Officer
Gindhart, Joseph G
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of Chicago
Schools of Medicine
United States
Zip Code
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