Abstract
Filamentous actin (F-actin) and non-muscle myosin II motors drive cell motility and cell shape changes that guide large scale tissue movements during embryonic morphogenesis. To gain a better understanding of the role of actomyosin in vivo, we have developed a two-dimensional (2D) computational model to study emergent phenomena of dynamic unbranched actomyosin arrays in the cell cortex. These phenomena include actomyosin punctuated contractions, or "actin asters" that form within quiescent F-actin networks. Punctuated contractions involve both formation of high intensity aster-like structures and disassembly of those same structures. Our 2D model allows us to explore the kinematics of filament polarity sorting, segregation of motors, and morphology of F-actin arrays that emerge as the model structure and biophysical properties are varied. Our model demonstrates the complex, emergent feedback between filament reorganization and motor transport that generate as well as disassemble actin asters. Since intracellular actomyosin dynamics are thought to be controlled by localization of scaffold proteins that bind F-actin or their myosin motors we also apply our 2D model to recapitulate in vitro studies that have revealed complex patterns of actomyosin that assemble from patterning filaments and motor complexes with microcontact printing. Although we use a minimal representation of filament, motor, and cross-linker biophysics, our model establishes a framework for investigating the role of other actin binding proteins, how they might alter actomyosin dynamics, and makes predictions that can be tested experimentally within live cells as well as within in vitro models.
Highlights
Recent genetic and mechanical studies of embryonic development reveal a critical role for intracellular scaffolds in generating the shape of the embryo and constructing internal
Dynamic actomyosin networks play a critical role in development by providing motive forces for cell shape change and morphogenesis, and by establishing tissue mechanical properties [1,2,3]
To understand how dynamic ordered arrays such as asters might emerge from disordered networks we developed a 2D "search, capture, remodel, and traffic" model that incorporates dynamic aspects of in vivo Filamentous actin (F-actin) and myosin motor interactions
Summary
Dynamic actomyosin networks play a critical role in development by providing motive forces for cell shape change and morphogenesis, and by establishing tissue mechanical properties [1,2,3]. In addition to regulating force or stress production actomyosin is responsible for establishing the mechanical properties of the embryo that resist stress and guide tissue deformation. Actomyosin controls much of the viscoelastic properties of Xenopus during gastrulation and neurulation as dorsal axial tissues converge and extend [8,9,10]. Wnt-signaling during mediolateral cell intercalation appears to control force production and stiffness by regulating F-actin polymerization and myosin II contractility [11, 12]. Surprisingly little is known about the mechanisms that coordinate the large-scale spatial and temporal dynamics of actomyosin network assembly and contraction during morphogenesis
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