A Physical Model of Cellular Symmetry Breaking

Gucht, Jasper van der; Sykes, Cécile

doi:10.1007/978-3-0346-0428-4_2

Cited by 7 publications

(7 citation statements)

References 47 publications

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“…Known from physics, but also of relevance in many molecular and cellular biology contexts (Li & Bowerman, 2010a, 2010bSoriano et al, 2009;van der Gucht & Sykes, 2009;Weiss et al, 2003), symmetry breaking occurs when extremely small stochastic fluctuations in a system eventually lead to the crossing of a threshold that determines which of two branches of a bifurcation (in possible states of the system) is taken. Due to symmetry breaking, a reaction-diffusion system can go from a nearly homogenous state to the spontaneous emergence of a stable and distinct structural pattern.…”

Section: About Here the Size Can Be Reduced So That It Does Not Takementioning

confidence: 99%

Systems biology and the integration of mechanistic explanation and mathematical explanation

Brigandt

2013

Studies in History and Philosophy of Science Part C: Studies in

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The paper discusses how systems biology is working toward complex accounts that integrate explanation in terms of mechanisms and explanation by mathematical models-which some philosophers have viewed as rival models of explanation. Systems biology is an integrative approach, and it strongly relies on mathematical modeling. Philosophical accounts of mechanisms capture integrative in the sense of multilevel and multifield explanations, yet accounts of mechanistic explanation (as the analysis of a whole in terms of its structural parts and their qualitative interactions) have failed to address how a mathematical model could contribute to such explanations. I discuss how mathematical equations can be explanatorily relevant. Several cases from systems biology are discussed to illustrate the interplay between mechanistic research and mathematical modeling, and I point to questions about qualitative phenomena (rather than the explanation of quantitative details), where quantitative models are still indispensable to the explanation. Systems biology shows that a broader philosophical conception of mechanisms is needed, which takes into account functional-dynamical aspects, interaction in complex networks with feedback loops, system-wide functional properties such as distributed functionality and robustness, and a mechanism's ability to respond to perturbations (beyond its actual operation). I offer general conclusions for philosophical accounts of explanation.

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Section: About Here the Size Can Be Reduced So That It Does Not Takementioning

confidence: 99%

Systems biology and the integration of mechanistic explanation and mathematical explanation

Brigandt

2013

Studies in History and Philosophy of Science Part C: Studies in

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“…One possibility is that it triggers the mechanical rupture of a prestressed cortical network, leading to the rapid discharge of stored mechanical stress. This type of mechanical instability is thought to drive symmetry breaking and directional motility of beads coated with agents that promote actin filament assembly in vitro (see van der Gucht andSykes 2009 andMullins 2009). It may also govern symmetry-breaking processes underlying directional actin-dependent motility of endosomes (Taunton et al 2000), chromosomes (Li et al 2008), and the episodic myosin-dependent collapse of the cell cortex that underlies shape oscillations in cellular fragments (Paluch et al 2005).…”

Section: Asymmetric Contraction and Cortical Flows Segregate Corticalmentioning

confidence: 99%

Cellular Symmetry Breaking during Caenorhabditis elegans Development

Munro

Bowerman²

2009

Cold Spring Harbor Perspectives in Biology

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The nematode worm Caenorhabditis elegans has produced a wellspring of insights into mechanisms that govern cellular symmetry breaking during animal development. Here we focus on two highly conserved systems that underlie many of the key symmetry-breaking events that occur during embryonic and larval development in the worm. One involves the interplay between Par proteins, Rho GTPases, and the actomyosin cytoskeleton and mediates asymmetric cell divisions that establish the germline. The other uses elements of the Wnt signaling pathway and a highly reiterative mechanism that distinguishes anterior from posterior daughter cell fates. Much of what we know about these systems comes from intensive study of a few key events-Par/Rho/actomyosin-mediated polarization of the zygote in response to a sperm-derived cue and the Wnt-mediated induction of endoderm at the four-cell stage. However, a growing body of work is revealing how C. elegans exploits elements/variants of these systems to accomplish a diversity of symmetry-breaking tasks throughout embryonic and larval development. Over the past few decades, the C. elegans embryo has become a premiere system for studying cellular symmetry breaking in a developmental context. During C. elegans development, nearly every division produces daughter cells with different developmental trajectories. In some cases, these differences are imposed on daughters before or after division through inductive signals, but many of these divisions are intrinsically asymmetric-an initial symmetry-breaking step creates polarized distributions or activities of factors that control developmental potential. Registration of the cleavage plane with the axis of polarity then ensures differential inheritance of these potentials. With respect to cell fates, the output of these asymmetric divisions is amazingly diverse, yet the embryo seems to accomplish this diversity through variants of a few conserved symmetry-breaking systems. Thus the C. elegans embryo provides an exceptional opportunity to explore not only the core mechanisms underlying cellular symmetry breaking, but also how evolution can reconfigure these mechanisms to do different but related jobs in multiple contexts.In this review, we focus most of our attention on two conserved systems that together Editors: Rong Li and Bruce Bowerman Additional Perspectives on Symmetry Breaking in Biology available at

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“…In this Letter, we demonstrate that asymmetry in the shape or the chemistry of the colloidal particle, assumed in most existing studies on autophoretic swimmers [13][14][15][16]18 , is not necessary for locomotion. We show that isotropic spherical particles can achieve self-propulsion through a spontaneous symmetry-breaking mechanism, a route to locomotion akin to that of a larger variety of biological systems 26 . We solve analytically the classical nonlinear autophoretic theoretical framework at arbitrary Péclet number.…”

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confidence: 99%

Spontaneous autophoretic motion of isotropic particles

2013

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Suspended colloidal particles interacting chemically with a solute can self-propel by autophoretic motion when they are asymmetrically patterned (Janus colloids). Here we demonstrate theoretically that such anisotropy is not necessary for locomotion and that the nonlinear interplay between surface osmotic flows and solute advection can produce spontaneous, and self-sustained motion of isotropic particles. Solving the classical autophoretic framework for isotropic particles, we show that, for given material properties, there exists a critical particle size (or Péclet number) above which spontaneous symmetry-breaking and autophoretic motion occur. A hierarchy of instabilities is further identified for quantized critical Péclet numbers.The locomotion of microorganisms has long been used as a motivation and a practical inspiration for the design of synthetic self-propelled particles. Typically, biological cells generate propulsion by deforming their slender appendages, termed flagella or cilia, in a non-time-reversible fashion 1 . However, and perhaps not surprisingly given the numerous microfabrication challenges, no genuinely self-propelled micro-swimmer has been manufactured in the lab so far. Instead, man-made biomimetic propellers are driven by external torques or forces. That actuation allows either to deform soft propellers whose deformed shape induce propulsion 2-4 , to continuously generate propulsion in chiral shapes 5,6 , or to exploit interactions with surfaces 7-9 .An alternative route for the production of artificial small-scale swimmers has proven to be much more successful. It consists in making miniaturized chemically powered "engines" with no moving parts, typically made of reactive Janus beads or rods 10-12 . The reaction products released by these chemically-asymmetric particles create concentration gradients which induce a net phoretic fluid motion near their surface leading to locomotion. Theoretically, the interest in these so-called autophoretic swimmers was triggered by a theoretical model which accounted for such a novel propulsion mechanism in a simple and generic fashion 13,14 . This model was then further elaborated to include the nonlinear interplay between the colloid motion and the advection of the reactants 15-17 or a more complex kinetic route for the surface chemistry 18 , to deal with the rotational Brownian motion of the swimmers 19 , and to detail the microscopic coupling between the concentration gradients and the fluid flows at small scales 20 .In order to self-propel, autophoretic swimmers are chemically patterned, and it is the asymmetries in the chemical reactions on their surfaces which are responsible for locomotion in the first place. This requirement would make it thus difficult to achieve high-throughput production. An ingenious solution to such an engineering issue was recently offered with the production of isotropic self-propelled Marangoni droplets 21 . In a mechanism akin to the one responsible for the spontaneous motion of reactive droplets surfing on fluid inter...

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A Physical Model of Cellular Symmetry Breaking

Cited by 7 publications

References 47 publications

Systems biology and the integration of mechanistic explanation and mathematical explanation

Systems biology and the integration of mechanistic explanation and mathematical explanation

Cellular Symmetry Breaking during Caenorhabditis elegans Development

Spontaneous autophoretic motion of isotropic particles

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