scholarly journals Actin-ring segment switching drives nonadhesive gap closure

2020 ◽  
Vol 117 (52) ◽  
pp. 33263-33271
Author(s):  
Qiong Wei ◽  
Xuechen Shi ◽  
Tiankai Zhao ◽  
Pingqiang Cai ◽  
Tianwu Chen ◽  
...  
Keyword(s):  
Large Scale ◽  
Traction Force ◽  
Collective Cell Migration ◽  
Actin Ring ◽  
Purse String ◽  
Actin Cable ◽  
Gap Closure ◽  
Actin Fiber ◽  
Ring Segment ◽  
Cable Segment

Gap closure to eliminate physical discontinuities and restore tissue integrity is a fundamental process in normal development and repair of damaged tissues and organs. Here, we demonstrate a nonadhesive gap closure model in which collective cell migration, large-scale actin-network fusion, and purse-string contraction orchestrate to restore the gap. Proliferative pressure drives migrating cells to attach onto the gap front at which a pluricellular actin ring is already assembled. An actin-ring segment switching process then occurs by fusion of actin fibers from the newly attached cells into the actin cable and defusion from the previously lined cells, thereby narrowing the gap. Such actin-cable segment switching occurs favorably at high curvature edges of the gap, yielding size-dependent gap closure. Cellular force microscopies evidence that a persistent rise in the radial component of inward traction force signifies successful actin-cable segment switching. A kinetic model that integrates cell proliferation, actin fiber fusion, and purse-string contraction is formulated to quantitatively account for the gap-closure dynamics. Our data reveal a previously unexplored mechanism in which cells exploit multifaceted strategies in a highly cooperative manner to close nonadhesive gaps.

Soil/Tire Interaction Analysis Using FEM and FVM

2005 ◽  
Vol 33 (1) ◽  
pp. 38-62 ◽  
Author(s):  
S. Oida ◽  
E. Seta ◽  
H. Heguri ◽  
K. Kato
Keyword(s):  
Large Scale ◽  
Interaction Analysis ◽  
Yield Criterion ◽  
Surrounding Medium ◽  
Flow Analysis ◽  
Measurement Data ◽  
Traction Force ◽  
Elastoplastic Material ◽  
The Road ◽  
Soil Flow

Abstract Vehicles, such as an agricultural tractor, construction vehicle, mobile machinery, and 4-wheel drive vehicle, are often operated on unpaved ground. In many cases, the ground is deformable; therefore, the deformation should be taken into consideration in order to assess the off-the-road performance of a tire. Recent progress in computational mechanics enabled us to simulate the large scale coupling problem, in which the deformation of tire structure and of surrounding medium can be interactively considered. Using this technology, hydroplaning phenomena and tire traction on snow have been predicted. In this paper, the simulation methodology of tire/soil coupling problems is developed for pneumatic tires of arbitrary tread patterns. The Finite Element Method (FEM) and the Finite Volume Method (FVM) are used for structural and for soil-flow analysis, respectively. The soil is modeled as an elastoplastic material with a specified yield criterion and a nonlinear elasticity. The material constants are referred to measurement data, so that the cone penetration resistance and the shear resistance are represented. Finally, the traction force of the tire in a cultivated field is predicted, and a good correlation with experiments is obtained.

scholarly journals Reconstitution of contractile actomyosin rings in vesicles

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Thomas Litschel ◽  
Charlotte F. Kelley ◽  
Danielle Holz ◽  
Maral Adeli Koudehi ◽  
Sven K. Vogel ◽  
...  
Keyword(s):  
Large Scale ◽  
Actin Polymerization ◽  
Living Cells ◽  
Actin Ring ◽  
Actin Networks ◽  
Mechanical Transformation ◽  
Myosin Motors ◽  
Spherical Vesicles ◽  
Theoretical Considerations ◽  
Encapsulation Methods

AbstractOne of the grand challenges of bottom-up synthetic biology is the development of minimal machineries for cell division. The mechanical transformation of large-scale compartments, such as Giant Unilamellar Vesicles (GUVs), requires the geometry-specific coordination of active elements, several orders of magnitude larger than the molecular scale. Of all cytoskeletal structures, large-scale actomyosin rings appear to be the most promising cellular elements to accomplish this task. Here, we have adopted advanced encapsulation methods to study bundled actin filaments in GUVs and compare our results with theoretical modeling. By changing few key parameters, actin polymerization can be differentiated to resemble various types of networks in living cells. Importantly, we find membrane binding to be crucial for the robust condensation into a single actin ring in spherical vesicles, as predicted by theoretical considerations. Upon force generation by ATP-driven myosin motors, these ring-like actin structures contract and locally constrict the vesicle, forming furrow-like deformations. On the other hand, cortex-like actin networks are shown to induce and stabilize deformations from spherical shapes.

PCR Based Strategies for Gap Closure in Large-scale Sequencing Projects

1994 ◽  
pp. 182-190 ◽  
Author(s):  
D.M. MUZNY ◽  
S. RICHARDS ◽  
Y. SHEN ◽  
R.A. GIBBS
Keyword(s):  
Large Scale ◽  
Gap Closure

scholarly journals The role of viscoelasticity in long-time cell rearrangement

2021 ◽  
Author(s):  
Ivana Pajic-Lijakovic ◽  
Milan Milivojevic
Keyword(s):  
Cell Monolayer ◽  
Traction Force ◽  
Surface Tension Force ◽  
Rheological Parameters ◽  
Collective Cell Migration ◽  
Tissue Stiffness ◽  
Free Expansion ◽  
Cell Rearrangement ◽  
Mechanical Waves ◽  
Rheological Modeling

Although collective cell migration (CCM) is a highly coordinated and ordered migratory mode, perturbations in the form of mechanical waves appear even in 2D. These perturbations caused by the viscoelastic nature of cell rearrangement are involved in various biological processes, such as embryogenesis, wound healing and cancer invasion. The mechanical waves, as a product of the active turbulence occurred at low Reynolds number, represent an oscillatory change in cell velocity and the relevant rheological parameters. The velocity oscillations, in the form of forward and backward flows, are driven by: viscoelastic force, surface tension force, and traction force. The viscoelastic force represents a consequence of inhomogeneous distribution of cell residual stress accumulated during CCM. This cause-consequence relation is considered on a model system such as the cell monolayer free expansion. The collision of forward and backward flows causes an increase in cell packing density which has a feedback impact on the tissue viscoelasticity and on that base influences the tissue stiffness. The evidence of how the tissue stiffness is changed near the cell jamming is conflicting. To fill this gap, we discussed the density driven change in the tissue viscoelasticity by accounting for the cell pseudo-phase transition from active (contractile) to passive (non-contractile) state appeared near cell jamming in the rheological modeling consideration.

scholarly journals Reconstitution of contractile actomyosin rings in vesicles

2020 ◽  
Author(s):  
Thomas Litschel ◽  
Charlotte F. Kelley ◽  
Danielle Holz ◽  
Maral Adeli Koudehi ◽  
Sven Kenjiro Vogel ◽  
...  
Keyword(s):  
Large Scale ◽  
Actin Polymerization ◽  
Living Cells ◽  
Actin Ring ◽  
Actin Networks ◽  
Mechanical Transformation ◽  
Myosin Motors ◽  
Spherical Vesicles ◽  
Theoretical Considerations ◽  
Encapsulation Methods

AbstractOne of the grand challenges of bottom-up synthetic biology is the development of minimal machineries for cell division. The mechanical transformation of large-scale compartments, such as Giant Unilamellar Vesicles (GUVs), requires the geometry-specific coordination of active elements, several orders of magnitude larger than the molecular scale. Of all cytoskeletal structures, large-scale actomyosin rings appear to be the most promising cellular elements to accomplish this task. Here, we have adopted advanced encapsulation methods to study bundled actin filaments in GUVs and compare our results with theoretical modeling. By changing few key parameters, actin polymerization can be differentiated to resemble various types of networks in living cells. Importantly, we find membrane binding to be crucial for the robust condensation into a single actin ring in spherical vesicles, as predicted by theoretical considerations. Upon force generation by ATP-driven myosin motors, these ring-like actin structures contract and locally constrict the vesicle, forming furrow-like deformations. On the other hand, cortex-like actin networks are shown to induce and stabilize deformations from spherical shapes.

scholarly journals Collective migration during a gap closure in a two-dimensional haptotactic model

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Marie Versaevel ◽  
Laura Alaimo ◽  
Valentine Seveau ◽  
Marine Luciano ◽  
Danahe Mohammed ◽  
...  
Keyword(s):  
Cell Migration ◽  
Cell Density ◽  
Healing Process ◽  
Time Lapse ◽  
Wound Healing Process ◽  
Collective Cell Migration ◽  
Two Dimensional ◽  
Gap Closure ◽  
Lower Cell Density ◽  
Protein Gradients

AbstractThe ability of cells to respond to substrate-bound protein gradients is crucial for many physiological processes, such as immune response, neurogenesis and cancer cell migration. However, the difficulty to produce well-controlled protein gradients has long been a limitation to our understanding of collective cell migration in response to haptotaxis. Here we use a photopatterning technique to create circular, square and linear fibronectin (FN) gradients on two-dimensional (2D) culture substrates. We observed that epithelial cells spread preferentially on zones of higher FN density, creating rounded or elongated gaps within epithelial tissues over circular or linear FN gradients, respectively. Using time-lapse experiments, we demonstrated that the gap closure mechanism in a 2D haptotaxis model requires a significant increase of the leader cell area. In addition, we found that gap closures are slower on decreasing FN densities than on homogenous FN-coated substrate and that fresh closed gaps are characterized by a lower cell density. Interestingly, our results showed that cell proliferation increases in the closed gap region after maturation to restore the cell density, but that cell–cell adhesive junctions remain weaker in scarred epithelial zones. Taken together, our findings provide a better understanding of the wound healing process over protein gradients, which are reminiscent of haptotaxis.

scholarly journals Directed Gap Closure in Large-Scale Sequencing Projects

2001 ◽  
Vol 11 (5) ◽  
pp. 901-903 ◽  
Author(s):  
M. Frohme ◽  
A. A. Camargo ◽  
C. Czink ◽  
A. Y. Matsukuma ◽  
A. J.G. Simpson ◽  
...  
Keyword(s):  
Large Scale ◽  
Gap Closure

scholarly journals Dynamic cellular finite-element method for modelling large-scale cell migration and proliferation under the control of mechanical and biochemical cues: a study of re-epithelialization

2017 ◽  
Vol 14 (129) ◽  
pp. 20160959 ◽  
Author(s):  
Jieling Zhao ◽  
Youfang Cao ◽  
Luisa A. DiPietro ◽  
Jie Liang
Keyword(s):  
Finite Element ◽  
Cell Migration ◽  
Large Scale ◽  
Full Range ◽  
Large Population ◽  
Computational Modelling ◽  
Cellular Protein ◽  
Collective Cell Migration ◽  
Cell Shapes ◽  
Cell Migration And Proliferation

Computational modelling of cells can reveal insight into the mechanisms of the important processes of tissue development. However, current cell models have limitations and are challenged to model detailed changes in cellular shapes and physical mechanics when thousands of migrating and interacting cells need to be modelled. Here we describe a novel dynamic cellular finite-element model (DyCelFEM), which accounts for changes in cellular shapes and mechanics. It also models the full range of cell motion, from movements of individual cells to collective cell migrations. The transmission of mechanical forces regulated by intercellular adhesions and their ruptures are also accounted for. Intra-cellular protein signalling networks controlling cell behaviours are embedded in individual cells. We employ DyCelFEM to examine specific effects of biochemical and mechanical cues in regulating cell migration and proliferation, and in controlling tissue patterning using a simplified re-epithelialization model of wound tissue. Our results suggest that biochemical cues are better at guiding cell migration with improved directionality and persistence, while mechanical cues are better at coordinating collective cell migration. Overall, DyCelFEM can be used to study developmental processes when a large population of migrating cells under mechanical and biochemical controls experience complex changes in cell shapes and mechanics.

scholarly journals Physiological Importance and Identification of Novel Targets for the N-Terminal Acetyltransferase NatB

2006 ◽  
Vol 5 (2) ◽  
pp. 368-378 ◽  
Author(s):  
Robert Caesar ◽  
Jonas Warringer ◽  
Anders Blomberg
Keyword(s):  
Cell Cycle ◽  
Protein Function ◽  
Large Scale ◽  
Cell Cycle Progression ◽  
Physiological Role ◽  
Phenotypic Analysis ◽  
Physiological Importance ◽  
Actin Cable ◽  
Actin Cables ◽  
Dna Processing

ABSTRACT The N-terminal acetyltransferase NatB in Saccharomyces cerevisiae consists of the catalytic subunit Nat3p and the associated subunit Mdm20p. We here extend our present knowledge about the physiological role of NatB by a combined proteomics and phenomics approach. We found that strains deleted for either NAT3 or MDM20 displayed different growth rates and morphologies in specific stress conditions, demonstrating that the two NatB subunits have partly individual functions. Earlier reported phenotypes of the nat3Δ strain have been associated with altered functionality of actin cables. However, we found that point mutants of tropomyosin that suppress the actin cable defect observed in nat3Δ only partially restores wild-type growth and morphology, indicating the existence of functionally important acetylations unrelated to actin cable function. Predicted NatB substrates were dramatically overrepresented in a distinct set of biological processes, mainly related to DNA processing and cell cycle progression. Three of these proteins, Cac2p, Pac10p, and Swc7p, were identified as true NatB substrates. To identify N-terminal acetylations potentially important for protein function, we performed a large-scale comparative phenotypic analysis including nat3Δ and strains deleted for the putative NatB substrates involved in cell cycle regulation and DNA processing. By this procedure we predicted functional importance of the N-terminal acetylation for 31 proteins.

scholarly journals Hindbrain neuropore tissue geometry determines asymmetric cell-mediated closure dynamics

2020 ◽  
Author(s):  
Eirini Maniou ◽  
Michael F Staddon ◽  
Abigail Marshall ◽  
Nicholas DE Greene ◽  
Andrew J Copp ◽  
...  
Keyword(s):  
Aspect Ratio ◽  
Leading Edge ◽  
Tissue Level ◽  
Purse String ◽  
Closure Rate ◽  
Surface Ectoderm ◽  
Gap Closure ◽  
Rate Asymmetry ◽  
Constant Rate ◽  
Tissue Geometry

AbstractGap closure is a common morphogenetic process. In mammals, failure to close the embryonic hindbrain neuropore (HNP) gap causes fatal anencephaly. We observed that surface ectoderm cells surrounding the mouse HNP assemble high-tension actomyosin purse-strings at their leading edge and establish the initial contacts across the embryonic midline. The HNP gap closes asymmetrically, faster from its rostral than caudal extreme, while maintaining an elongated aspect ratio. Cell-based physical modelling identifies two closure mechanisms sufficient to describe tissue-level HNP closure dynamics; purse-string contraction and directional cell crawling. Combining both closure mechanisms hastens gap closure and produces a constant rate of gap shortening. Purse-string contraction reduces, whereas crawling increases gap aspect ratio, and their combination maintains it. Closure rate asymmetry can be explained by embryo tissue geometry, namely a narrower rostral gap apex. At the cellular level, our model predicts highly directional cell migration with a constant rate of cells leaving the HNP rim. These behaviours are reproducibly live-imaged in mouse embryos. Thus, mammalian embryos coordinate cellular and tissue-level mechanics to achieve this critical gap closure event.

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