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Floyd C, Levine H, Jarzynski C, Papoian GA. Understanding cytoskeletal avalanches using mechanical stability analysis. Proc Natl Acad Sci U S A 2021; 118:e2110239118. [PMID: 34611021 PMCID: PMC8521716 DOI: 10.1073/pnas.2110239118] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/24/2021] [Indexed: 12/28/2022] Open
Abstract
Eukaryotic cells are mechanically supported by a polymer network called the cytoskeleton, which consumes chemical energy to dynamically remodel its structure. Recent experiments in vivo have revealed that this remodeling occasionally happens through anomalously large displacements, reminiscent of earthquakes or avalanches. These cytoskeletal avalanches might indicate that the cytoskeleton's structural response to a changing cellular environment is highly sensitive, and they are therefore of significant biological interest. However, the physics underlying "cytoquakes" is poorly understood. Here, we use agent-based simulations of cytoskeletal self-organization to study fluctuations in the network's mechanical energy. We robustly observe non-Gaussian statistics and asymmetrically large rates of energy release compared to accumulation in a minimal cytoskeletal model. The large events of energy release are found to correlate with large, collective displacements of the cytoskeletal filaments. We also find that the changes in the localization of tension and the projections of the network motion onto the vibrational normal modes are asymmetrically distributed for energy release and accumulation. These results imply an avalanche-like process of slow energy storage punctuated by fast, large events of energy release involving a collective network rearrangement. We further show that mechanical instability precedes cytoquake occurrence through a machine-learning model that dynamically forecasts cytoquakes using the vibrational spectrum as input. Our results provide a connection between the cytoquake phenomenon and the network's mechanical energy and can help guide future investigations of the cytoskeleton's structural susceptibility.
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Affiliation(s)
- Carlos Floyd
- Biophysics Program, University of Maryland, College Park, MD 20742
| | - Herbert Levine
- Center for Theoretical Biological Physics, Northeastern University, Boston, MA 02115
- Department of Physics, Northeastern University, Boston, MA 02115
- Department of Bioengineering, Northeastern University, Boston, MA 02115
| | - Christopher Jarzynski
- Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742;
- Institute for Physical Science and Technology, University of Maryland, College Park, MD 20742
- Department of Physics, University of Maryland, College Park, MD 20742
| | - Garegin A Papoian
- Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742;
- Institute for Physical Science and Technology, University of Maryland, College Park, MD 20742
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Ediger MD, Gruebele M, Lubchenko V, Wolynes PG. Glass Dynamics Deep in the Energy Landscape. J Phys Chem B 2021; 125:9052-9068. [PMID: 34357766 DOI: 10.1021/acs.jpcb.1c01739] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
When a liquid is cooled, progress down the energy landscape is arrested near the glass transition temperature Tg. In principle, lower energy states can be accessed by waiting for further equilibration, but the rough energy landscape of glasses quickly leads to kinetics on geologically slow time scales below Tg. Over the past decade, progress has been made probing deeper into the energy landscape via several techniques. By looking at bulk and surface diffusion, using layered deposition that promotes equilibration, imaging glass surfaces with faster dynamics below Tg, and optically exciting glasses, experiments have moved into a regime of ultrastable, low energy glasses that was difficult to access in the past. At the same time, both simulations and energy landscape theory based on a random first order transition (RFOT) have tackled systems that include surfaces, optical excitation, and interfacial dynamics. Here we review some of the recent experimental work, and how energy landscape theory illuminates glassy dynamics well below the glass transition temperature by making direct connections between configurational entropy, energy landscape barriers, and the resulting dynamics.
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Affiliation(s)
- Mark D Ediger
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States
| | - Martin Gruebele
- Department of Chemistry, Department of Physics, Center for Biophysics and Quantitative Biology, and Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Champaign, Illinois 61801, United States
| | - Vassiliy Lubchenko
- Departments of Chemistry and Physics, and the Center for Superconductivity, University of Houston, Houston, Texas 77204, United States
| | - Peter G Wolynes
- Departments of Chemistry, Physics and Astronomy, Biosciences, Materials Science and Nanoengineering, and the Center for Theoretical Biological Physics, Rice University, Houston, Texas 77005, United States
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Sadhukhan S, Nandi SK. Theory and simulation for equilibrium glassy dynamics in cellular Potts model of confluent biological tissue. Phys Rev E 2021; 103:062403. [PMID: 34271700 DOI: 10.1103/physreve.103.062403] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Accepted: 05/14/2021] [Indexed: 01/23/2023]
Abstract
Glassy dynamics in a confluent monolayer is indispensable in morphogenesis, wound healing, bronchial asthma, and many others; a detailed theoretical framework for such a system is, therefore, important. Vertex-model (VM) simulations have provided crucial insights into the dynamics of such systems, but their nonequilibrium nature makes theoretical development difficult. The cellular Potts model (CPM) of confluent monolayers provides an alternative model for such systems with a well-defined equilibrium limit. We combine numerical simulations of the CPM and an analytical study based on one of the most successful theories of equilibrium glass, the random first-order transition theory, and develop a comprehensive theoretical framework for a confluent glassy system. We find that the glassy dynamics within the CPM is qualitatively similar to that in the VM. Our study elucidates the crucial role of geometric constraints in bringing about two distinct regimes in the dynamics, as the target perimeter P_{0} is varied. The unusual sub-Arrhenius relaxation results from the distinctive interaction potential arising from the perimeter constraint in such systems. The fragility of the system decreases with increasing P_{0} in the low-P_{0} regime, whereas the dynamics is independent of P_{0} in the other regime. The rigidity transition, found in the VM, is absent within the CPM; this difference seems to come from the nonequilibrium nature of the former. We show that the CPM captures the basic phenomenology of glassy dynamics in a confluent biological system via comparison of our numerical results with existing experiments on different systems.
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Affiliation(s)
- Souvik Sadhukhan
- TIFR Centre for Interdisciplinary Sciences, Tata Institute of Fundamental Research, Hyderabad 500046, India
| | - Saroj Kumar Nandi
- TIFR Centre for Interdisciplinary Sciences, Tata Institute of Fundamental Research, Hyderabad 500046, India
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The role of the Arp2/3 complex in shaping the dynamics and structures of branched actomyosin networks. Proc Natl Acad Sci U S A 2020; 117:10825-10831. [PMID: 32354995 DOI: 10.1073/pnas.1922494117] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Actomyosin networks give cells the ability to move and divide. These networks contract and expand while being driven by active energy-consuming processes such as motor protein walking and actin polymerization. Actin dynamics is also regulated by actin-binding proteins, such as the actin-related protein 2/3 (Arp2/3) complex. This complex generates branched filaments, thereby changing the overall organization of the network. In this work, the spatiotemporal patterns of dynamical actin assembly accompanying the branching-induced reorganization caused by Arp2/3 were studied using a computational model (mechanochemical dynamics of active networks [MEDYAN]); this model simulates actomyosin network dynamics as a result of chemical reactions whose rates are modulated by rapid mechanical equilibration. We show that branched actomyosin networks relax significantly more slowly than do unbranched networks. Also, branched networks undergo rare convulsive movements, "avalanches," that release strain in the network. These avalanches are associated with the more heterogeneous distribution of mechanically linked filaments displayed by branched networks. These far-from-equilibrium events arising from the marginal stability of growing actomyosin networks provide a possible mechanism of the "cytoquakes" recently seen in experiments.
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Alvarado J, Cipelletti L, Koenderink GH. Uncovering the dynamic precursors to motor-driven contraction of active gels. SOFT MATTER 2019; 15:8552-8565. [PMID: 31637398 DOI: 10.1039/c9sm01172b] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Cells and tissues have the remarkable ability to actively generate the forces required to change their shape. This active mechanical behavior is largely mediated by the actin cytoskeleton, a crosslinked network of actin filaments that is contracted by myosin motors. Experiments and active gel theories have established that the length scale over which gel contraction occurs is governed by a balance between molecular motor activity and crosslink density. By contrast, the dynamics that govern the contractile activity of the cytoskeleton remain poorly understood. Here we investigate the microscopic dynamics of reconstituted actin-myosin networks using simultaneous real-space video microscopy and Fourier-space dynamic light scattering. Light scattering reveals different regimes of microscopic dynamics as a function of sample age. We uncover two dynamical precursors that precede macroscopic gel contraction. One is characterized by a progressive acceleration of stress-induced rearrangements, while the other consists of sudden, heterogeneous rearrangements. Intriguingly, our findings suggest a qualitative analogy between self-driven rupture and collapse of active gels and the delayed rupture of passive gels observed in earlier studies of colloidal gels under external loads.
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Affiliation(s)
- José Alvarado
- AMOLF, Living Matter Department, 1098 XG Amsterdam, The Netherlands.
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Nandi SK, Gov NS. Effective temperature of active fluids and sheared soft glassy materials. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2018; 41:117. [PMID: 30302578 DOI: 10.1140/epje/i2018-11731-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2018] [Accepted: 09/12/2018] [Indexed: 06/08/2023]
Abstract
The dynamics within active fluids, driven by internal activity of the self-propelled particles, is a subject of intense study in non-equilibrium physics. These systems have been explored using simulations, where the motion of a passive tracer particle is followed. Similar studies have been carried out for a soft glassy material that is driven by shearing its boundaries. In both types of systems the non-equilibrium motion have been quantified by defining a set of "effective temperatures", using both the tracer particle kinetic energy and the fluctuation-dissipation relation. We demonstrate that these effective temperatures extracted from the many-body simulations fit analytical expressions that are obtained for a single active particle inside a visco-elastic fluid. This result provides testable predictions and suggests a unified description for the dynamics inside active systems.
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Affiliation(s)
- Saroj Kumar Nandi
- Department of Chemical and Biological Physics, The Weizmann Institute of Science, 76100, Rehovot, Israel
| | - N S Gov
- Department of Chemical and Biological Physics, The Weizmann Institute of Science, 76100, Rehovot, Israel.
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Abstract
How does nonequilibrium activity modify the approach to a glass? This is an important question, since many experiments reveal the near-glassy nature of the cell interior, remodeled by activity. However, different simulations of dense assemblies of active particles, parametrized by a self-propulsion force, [Formula: see text], and persistence time, [Formula: see text], appear to make contradictory predictions about the influence of activity on characteristic features of glass, such as fragility. This calls for a broad conceptual framework to understand active glasses; here, we extend the random first-order transition (RFOT) theory to a dense assembly of self-propelled particles. We compute the active contribution to the configurational entropy through an effective model of a single particle in a caging potential. This simple active extension of RFOT provides excellent quantitative fits to existing simulation results. We find that whereas [Formula: see text] always inhibits glassiness, the effect of [Formula: see text] is more subtle and depends on the microscopic details of activity. In doing so, the theory automatically resolves the apparent contradiction between the simulation models. The theory also makes several testable predictions, which we verify by both existing and new simulation data, and should be viewed as a step toward a more rigorous analytical treatment of active glass.
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Nandi SK. Activity-dependent self-regulation of viscous length scales in biological systems. Phys Rev E 2018; 97:052404. [PMID: 29906984 DOI: 10.1103/physreve.97.052404] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Indexed: 06/08/2023]
Abstract
The cellular cortex, which is a highly viscous thin cytoplasmic layer just below the cell membrane, controls the cell's mechanical properties, which can be characterized by a hydrodynamic length scale ℓ. Cells actively regulate ℓ via the activity of force-generating molecules, such as myosin II. Here we develop a general theory for such systems through a coarse-grained hydrodynamic approach including activity in the static description of the system providing an experimentally accessible parameter and elucidate the detailed mechanism of how a living system can actively self-regulate its hydrodynamic length scale, controlling the rigidity of the system. Remarkably, we find that ℓ, as a function of activity, behaves universally and roughly inversely proportional to the activity of the system. Our theory rationalizes a number of experimental findings on diverse systems, and comparison of our theory with existing experimental data shows good agreement.
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Affiliation(s)
- Saroj Kumar Nandi
- Max-Planck Institute für Physik Komplexer Systeme, 01187 Dresden, Germany
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Nandi SK, Gov NS. Nonequilibrium mode-coupling theory for dense active systems of self-propelled particles. SOFT MATTER 2017; 13:7609-7616. [PMID: 29028064 DOI: 10.1039/c7sm01648d] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The physics of active systems of self-propelled particles, in the regime of a dense liquid state, is an open puzzle of great current interest, both for statistical physics and because such systems appear in many biological contexts. We develop a nonequilibrium mode-coupling theory (MCT) for such systems, where activity is included as a colored noise with the particles having a self-propulsion force f0 and a persistence time τp. Using the extended MCT and a generalized fluctuation-dissipation theorem, we calculate the effective temperature Teff of the active fluid. The nonequilibrium nature of the systems is manifested through a time-dependent Teff that approaches a constant in the long-time limit, which depends on the activity parameters f0 and τp. We find, phenomenologically, that this long-time limit is captured by the potential energy of a single, trapped active particle (STAP). Through a scaling analysis close to the MCT glass transition point, we show that τα, the α-relaxation time, behaves as τα ∼ f0-2γ, where γ = 1.74 is the MCT exponent for the passive system. τα may increase or decrease as a function of τp depending on the type of active force correlations, but the behavior is always governed by the same value of the exponent γ. Comparison with the numerical solution of the nonequilibrium MCT and simulation results give excellent agreement with scaling analysis.
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Affiliation(s)
- Saroj Kumar Nandi
- Department of Materials and Interfaces, The Weizmann Institute of Science, P.O. Box 26, 234 Herzl Street, Rehovot 7610001, Israel.
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Affiliation(s)
- Xiaoyu Bai
- Department of Chemistry and Center for Theoretical Biological Physics, Rice University, Houston, Texas 77005, USA
| | - Peter G. Wolynes
- Department of Chemistry and Center for Theoretical Biological Physics, Rice University, Houston, Texas 77005, USA
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Sadati M, Nourhani A, Fredberg JJ, Qazvini NT. Glass-like dynamics in the cell and in cellular collectives. WILEY INTERDISCIPLINARY REVIEWS. SYSTEMS BIOLOGY AND MEDICINE 2014; 6:137-49. [PMID: 24431332 PMCID: PMC4000035 DOI: 10.1002/wsbm.1258] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2013] [Revised: 10/21/2013] [Accepted: 12/02/2013] [Indexed: 01/19/2023]
Abstract
Prominent fluctuations, heterogeneity, and cooperativity dominate the dynamics of the cytoskeleton as well as the dynamics of the cellular collective. Such systems are out of equilibrium, disordered, and remain poorly understood. To explain these findings, we consider a unifying mechanistic rubric that imagines these systems as comprising phases of soft condensed matter in proximity to a glass or jamming transition, with associated transitions between solid-like versus liquid-like phases. At the scale of the cytoskeleton, data suggest that intermittent dynamics, kinetic arrest, and dynamic heterogeneity represent mesoscale features of glassy protein-protein interactions that link underlying biochemical events to integrative cellular behaviors such as crawling, contraction, and remodeling. At the scale of the multicellular collective, jamming has the potential to unify diverse biological factors that previously had been considered mostly as acting separately and independently. Although a quantitative relationship between intra- and intercellular dynamics is still lacking, glassy dynamics and jamming offer insights linking the mechanobiology of cell to human physiology and pathophysiology.
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Affiliation(s)
- Monirosadat Sadati
- School of Public Health, Harvard University, Boston, MA 02115, United States
| | - Amir Nourhani
- Department of Physics, The Pennsylvania State University, University Park, PA 16802, United States
| | - Jeffrey J. Fredberg
- School of Public Health, Harvard University, Boston, MA 02115, United States
| | - Nader Taheri Qazvini
- School of Public Health, Harvard University, Boston, MA 02115, United States, School of Chemistry, College of Science, University of Tehran, Tehran, Iran
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12
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Wang S, Wolynes PG. Active patterning and asymmetric transport in a model actomyosin network. J Chem Phys 2013; 139:235103. [PMID: 24359394 DOI: 10.1063/1.4848657] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Cytoskeletal networks, which are essentially motor-filament assemblies, play a major role in many developmental processes involving structural remodeling and shape changes. These are achieved by nonequilibrium self-organization processes that generate functional patterns and drive intracellular transport. We construct a minimal physical model that incorporates the coupling between nonlinear elastic responses of individual filaments and force-dependent motor action. By performing stochastic simulations we show that the interplay of motor processes, described as driving anti-correlated motion of the network vertices, and the network connectivity, which determines the percolation character of the structure, can indeed capture the dynamical and structural cooperativity which gives rise to diverse patterns observed experimentally. The buckling instability of individual filaments is found to play a key role in localizing collapse events due to local force imbalance. Motor-driven buckling-induced node aggregation provides a dynamic mechanism that stabilizes the two-dimensional patterns below the apparent static percolation limit. Coordinated motor action is also shown to suppress random thermal noise on large time scales, the two-dimensional configuration that the system starts with thus remaining planar during the structural development. By carrying out similar simulations on a three-dimensional anchored network, we find that the myosin-driven isotropic contraction of a well-connected actin network, when combined with mechanical anchoring that confers directionality to the collective motion, may represent a novel mechanism of intracellular transport, as revealed by chromosome translocation in the starfish oocyte.
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Affiliation(s)
- Shenshen Wang
- Department of Chemical Engineering and Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Peter G Wolynes
- Department of Chemistry and Center for Theoretical Biological Physics, Rice University, Houston, Texas 77005, USA
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Hardin C, Rajendran K, Manomohan G, Tambe DT, Butler JP, Fredberg JJ, Martinelli R, Carman CV, Krishnan R. Glassy dynamics, cell mechanics, and endothelial permeability. J Phys Chem B 2013; 117:12850-6. [PMID: 23638866 DOI: 10.1021/jp4020965] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
A key feature of all inflammatory processes is disruption of the vascular endothelial barrier. Such disruption is initiated in part through active contraction of the cytoskeleton of the endothelial cell (EC). Because contractile forces are propagated from cell to cell across a great many cell-cell junctions, this contractile process is strongly cooperative and highly nonlocal. We show here that the characteristic length scale of propagation is modulated by agonists and antagonists that impact permeability of the endothelial barrier. In the presence of agonists including thrombin, histamine, and H2O2, force correlation length increases, whereas in the presence of antagonists including sphingosine-1-phosphate, hepatocyte growth factor, and the rho kinase inhibitor, Y27632, force correlation length decreases. Intercellular force chains and force clusters are also evident, both of which are reminiscent of soft glassy materials approaching a glass transition.
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Affiliation(s)
- Corey Hardin
- Division of Pulmonary and Critical Care Medicine, Massachusetts General Hospital , Boston, Massachusetts
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