TY - JOUR A1 - Huber, Florian A1 - Schnauß, Jörg A1 - Rönicke, S. A1 - Rauch, P. A1 - Müller, K. A1 - Fütterer, C. A1 - Käs, Josef T1 - Emergent complexity of the cytoskeleton: from single filaments to tissue JF - Advances in Physics N2 - Despite their overwhelming complexity, living cells display a high degree of internal mechanical and functional organization which can largely be attributed to the intracellular biopolymer scaffold, the cytoskeleton. Being a very complex system far from thermodynamic equilibrium, the cytoskeleton's ability to organize is at the same time challenging and fascinating. The extensive amounts of frequently interacting cellular building blocks and their inherent multifunctionality permits highly adaptive behavior and obstructs a purely reductionist approach. Nevertheless (and despite the field's relative novelty), the physics approach has already proved to be extremely successful in revealing very fundamental concepts of cytoskeleton organization and behavior. This review aims at introducing the physics of the cytoskeleton ranging from single biopolymer filaments to multicellular organisms. Throughout this wide range of phenomena, the focus is set on the intertwined nature of the different physical scales (levels of complexity) that give rise to numerous emergent properties by means of self-organization or self-assembly. Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:due62-opus-34812 UR - http://www.ncbi.nlm.nih.gov/pubmed/24748680 SN - 1460-6976 N1 - Acknowledgment: We thank Klaus Kroy, Dan Strehle, Tobias Kießling, Matti Gralka, Harald Herrmann, Denis Wirtz, and Michael Höckel for very helpful comments, discussions, and proof reading. We further like to thank Steve Pawlizak, Thomas Fuhs, Daniel Koch, BjöStuhrmann, and Franziska Wetzel for contributing data and additional illustrations. This work was supported by the graduate school “Building with Molecules and Nano-Objects” (BuildMoNa). VL - 62 IS - 1 SP - 1 EP - 112 PB - Taylor & Francis ER - TY - JOUR A1 - Huber, Florian A1 - Strehle, Dan A1 - Schnauß, Jörg A1 - Käs, Josef T1 - Formation of regularly spaced networks as a general feature of actin bundle condensation by entropic forces JF - New Journal of Physics KW - DOAJ Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:due62-opus-34833 SN - 1367-2630 VL - 17 IS - 4 PB - IOP Publishing ER - TY - JOUR A1 - Huber, Florian A1 - Käs, Josef A1 - Stuhrmann, Björn T1 - Growing actin networks form lamellipodium and lamellum by self-assembly JF - Biophysical Journal N2 - Many different cell types are able to migrate by formation of a thin actin-based cytoskeletal extension. Recently, it became evident that this extension consists of two distinct substructures, designated lamellipodium and lamellum, which differ significantly in their kinetic and kinematic properties as well as their biochemical composition. We developed a stochastic two-dimensional computer simulation that includes chemical reaction kinetics, G-actin diffusion, and filament transport to investigate the formation of growing actin networks in migrating cells. Model parameters were chosen based on experimental data or theoretical considerations. In this work, we demonstrate the system's ability to form two distinct networks by self-organization. We found a characteristic transition in mean filament length as well as a distinct maximum in depolymerization flux, both within the first 1-2 microm. The separation into two distinct substructures was found to be extremely robust with respect to initial conditions and variation of model parameters. We quantitatively investigated the complex interplay between ADF/cofilin and tropomyosin and propose a plausible mechanism that leads to spatial separation of, respectively, ADF/cofilin- or tropomyosin-dominated compartments. Tropomyosin was found to play an important role in stabilizing the lamellar actin network. Furthermore, the influence of filament severing and annealing on the network properties is explored, and simulation data are compared to existing experimental data. KW - Open Archive Y1 - 2008 UR - http://www.ncbi.nlm.nih.gov/pubmed/18708450 U6 - https://doi.org/10.1529/biophysj.108.134817 SN - 1542-0086 VL - 95 IS - 12 SP - 5508 EP - 5523 PB - Biophysical Society ER - TY - JOUR A1 - Huber, Florian A1 - Käs, Josef T1 - Self-regulative organization of the cytoskeleton JF - Cytoskeleton N2 - Despite its impressive complexity the cytoskeleton succeeds to persistently organize itself and thus the cells' interior. In contrast to classical man-made machines, much of the cellular organization originates from inherent self-assembly and self-organization allowing a high degree of autonomy for various functional units. Recent experimental and theoretical studies revealed numerous examples of cytoskeleton components that arrange and organize in a self-regulative way. In the present review we want to shortly summarize some of the principle mechanisms that are able to inherently trigger and regulate the cytoskeleton organization. Although taken individually most of these regulative principles are rather simple with intuitively predictable consequences, combinations of two or more of these mechanisms can quickly give rise to very complex, unexpected behavior and might even be able to explain the formation of different functional units out of a common pool of available building blocks. Y1 - 2011 UR - http://www.ncbi.nlm.nih.gov/pubmed/21438165 U6 - https://doi.org/10.1002/cm.20509 SN - 1949-3592 N1 - Acknowledgment We would like to thank Dan Strehle for critical reading ofthis manuscript. This work was funded by the Leipzig School of Natural Sciences ‘‘BuildMoNa’’ as well as bythe Sa¨chsische Aufbaubank project number 13403 VL - 68 IS - 5 SP - 259 EP - 265 PB - Wiley ER - TY - JOUR A1 - Stuhrmann, Björn A1 - Huber, Florian A1 - Käs, Josef T1 - Robust organizational principles of protrusive biopolymer networks in migrating living cells JF - Plos One N2 - Cell migration is associated with the dynamic protrusion of a thin actin-based cytoskeletal extension at the cell front, which has been shown to consist of two different substructures, the leading lamellipodium and the subsequent lamellum. While the formation of the lamellipodium is increasingly well understood, organizational principles underlying the emergence of the lamellum are just beginning to be unraveled. We report here on a 1D mathematical model which describes the reaction-diffusion processes of a polarized actin network in steady state, and reproduces essential characteristics of the lamellipodium-lamellum system. We observe a steep gradient in filament lengths at the protruding edge, a local depolymerization maximum a few microns behind the edge, as well as a differential dominance of the network destabilizer ADF/cofilin and the stabilizer tropomyosin. We identify simple and robust organizational principles giving rise to the derived network characteristics, uncoupled from the specifics of any molecular implementation, and thus plausibly valid across cell types. An analysis of network length dependence on physico-chemical system parameters implies that to limit array treadmilling to cellular dimensions, network growth has to be truncated by mechanisms other than aging-induced depolymerization, e.g., by myosin-associated network dissociation at the transition to the cell body. Our work contributes to the analytical understanding of the cytoskeletal extension's bisection into lamellipodium and lamellum and sheds light on how cells organize their molecular machinery to achieve motility. KW - DOAJ Y1 - 2011 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:due62-opus-34901 SN - 1932-6203 N1 - Funding: This work has been supported by the Leipzig Graduate College ‘‘GK 1097 InterNeuro - Interdisciplinary Approaches in Cellular Neuroscience’’ (http:// www.uni-leipzig.de/˜ineuro/) and the Graduate School ‘‘Leipzig School of Natural Sciences - Building with Molecules and Nano-objects (BuildMoNa)’’ (http://www. buildmona.de/). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. VL - 6 IS - 1 PB - Public Library of Science (PLoS) ER - TY - JOUR A1 - Smith, David A1 - Gentry, Brian A1 - Stuhrmann, Björn A1 - Huber, Florian A1 - Strehle, D. A.N. A1 - Brunner, Claudia A1 - Koch, Daniel A1 - Steinbeck, Matthias A1 - Betz, Timo A1 - Käs, Josef A. T1 - The cytoskeleton: An active polymer-based scaffold JF - Biophysical Reviews and Letters Y1 - 2009 U6 - https://doi.org/10.1142/S1793048009000983 SN - 1793-7035 VL - 04 SP - 179 EP - 208 ER -