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Abdellatef SA, Wang H, Nakanishi J. Microtubules Disruption Alters the Cellular Structures and Mechanics Depending on Underlying Chemical Cues. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024:e2312282. [PMID: 39344221 DOI: 10.1002/smll.202312282] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2023] [Revised: 09/19/2024] [Indexed: 10/01/2024]
Abstract
The extracellular matrix determines cell morphology and stiffness by manipulating the cytoskeleton. The impacts of extracellular matrix cues, including the mechanical and topographical cues on microtubules and their role in biological behaviors, are previously studied. However, there is a lack of understanding about how microtubules (MTs) are affected by environmental chemical cues, such as extracellular matrix density. Specifically, it is crucial to understand the connection between cellular morphology and mechanics induced by chemical cues and the role of microtubules in these cellular responses. To address this, surfaces with high and low cRGD (cyclic Arginine-Glycine-Aspartic acid) peptide ligand densities are used. The cRGD is diluted with a bioinert ligand to prevent surface native cellular remodeling. The cellular morphology, actin, and microtubules differ on these surfaces. Confocal fluorescence microscopes and atomic force microscopy (AFM) are used to determine the structural and mechanical cellular responses with and without microtubules. Microtubules are vital as an intracellular scaffold in elongated morphology correlated with low cRGD compared to rounded morphology in high cRGD substrates. The contributions of MTs to nucleus morphology and cellular mechanics are based on the underlying cRGD densities. Finally, this study reveals a significant correlation between MTs, actin networks, and vimentin in response to the underlying densities of cRGD.
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Affiliation(s)
- Shimaa A Abdellatef
- Research Center for Macromolecules and Biomaterials, National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Hongxin Wang
- Research Center for Macromolecules and Biomaterials, National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Jun Nakanishi
- Research Center for Macromolecules and Biomaterials, National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, 305-0044, Japan
- Graduate School of Advanced Engineering, Tokyo University of Science, 6-3-1, Niijuku, Katsushika-ku, Tokyo, 125-8585, Japan
- Graduate School of Advanced Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo, 169-8555, Japan
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2
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Sankhe CS, Sacco JL, Lawton J, Fair RA, Soares DVR, Aldahdooh MKR, Gomez ED, Gomez EW. Breast Cancer Cells Exhibit Mesenchymal-Epithelial Plasticity Following Dynamic Modulation of Matrix Stiffness. Adv Biol (Weinh) 2024:e2400087. [PMID: 38977422 DOI: 10.1002/adbi.202400087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2024] [Revised: 05/31/2024] [Indexed: 07/10/2024]
Abstract
Mesenchymal-epithelial transition (MET) is essential for tissue and organ development and is thought to contribute to cancer by enabling the establishment of metastatic lesions. Despite its importance in both health and disease, there is a lack of in vitro platforms to study MET and little is known about the regulation of MET by mechanical cues. Here, hyaluronic acid-based hydrogels with dynamic and tunable stiffnesses mimicking that of normal and tumorigenic mammary tissue are synthesized. The platform is then utilized to examine the response of mammary epithelial cells and breast cancer cells to dynamic modulation of matrix stiffness. Gradual softening of the hydrogels reduces proliferation and increases apoptosis of breast cancer cells. Moreover, breast cancer cells exhibit temporal changes in cell morphology, cytoskeletal organization, and gene expression that are consistent with mesenchymal-epithelial plasticity as the stiffness of the matrix is reduced. A reduction in matrix stiffness attenuates the expression of integrin-linked kinase, and inhibition of integrin-linked kinase impacts proliferation, apoptosis, and gene expression in cells cultured on stiff and dynamic hydrogels. Overall, these findings reveal intermediate epithelial/mesenchymal states as cells move along a matrix stiffness-mediated MET trajectory and suggest an important role for matrix mechanics in regulating mesenchymal-epithelial plasticity.
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Affiliation(s)
- Chinmay S Sankhe
- Department of Chemical Engineering, The Pennsylvania State University, University Park, PA, 16802, USA
| | - Jessica L Sacco
- Department of Chemical Engineering, The Pennsylvania State University, University Park, PA, 16802, USA
| | - Jacob Lawton
- Department of Chemical Engineering, The Pennsylvania State University, University Park, PA, 16802, USA
| | - Ryan A Fair
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA, 16802, USA
| | | | - Mohammed K R Aldahdooh
- Department of Chemistry, The Pennsylvania State University, University Park, PA, 16802, USA
| | - Enrique D Gomez
- Department of Chemical Engineering, The Pennsylvania State University, University Park, PA, 16802, USA
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA, 16802, USA
| | - Esther W Gomez
- Department of Chemical Engineering, The Pennsylvania State University, University Park, PA, 16802, USA
- Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA, 16802, USA
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3
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Suzuki M, Yasue N, Ueno N. Differential cellular stiffness across tissues that contribute to Xenopus neural tube closure. Dev Growth Differ 2024; 66:320-328. [PMID: 38925637 PMCID: PMC11457508 DOI: 10.1111/dgd.12936] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2024] [Revised: 06/10/2024] [Accepted: 06/13/2024] [Indexed: 06/28/2024]
Abstract
During the formation of the neural tube, the primordium of the vertebrate central nervous system, the actomyosin activity of cells in different regions drives neural plate bending. However, how the stiffness of the neural plate and surrounding tissues is regulated and mechanically influences neural plate bending has not been elucidated. Here, we used atomic force microscopy to reveal the relationship between the stiffness of the neural plate and the mesoderm during Xenopus neural tube formation. Measurements with intact embryos revealed that the stiffness of the neural plate was consistently higher compared with the non-neural ectoderm and that it increased in an actomyosin activity-dependent manner during neural plate bending. Interestingly, measurements of isolated tissue explants also revealed that the relationship between the stiffness of the apical and basal sides of the neural plate was reversed during bending and that the stiffness of the mesoderm was lower than that of the basal side of the neural plate. The experimental elevation of mesoderm stiffness delayed neural plate bending, suggesting that low mesoderm stiffness mechanically supports neural tube closure. This study provides an example of mechanical interactions between tissues during large-scale morphogenetic movements.
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Affiliation(s)
- Makoto Suzuki
- Amphibian Research Center, Graduate School of Integrated Sciences for LifeHiroshima UniversityHiroshimaJapan
- Division of Morphogenesis, National Institute for Basic BiologyNational Institutes of Natural SciencesAichiJapan
- Basic Biology Programthe Graduate University of Advanced StudiesAichiJapan
| | - Naoko Yasue
- Division of Morphogenesis, National Institute for Basic BiologyNational Institutes of Natural SciencesAichiJapan
| | - Naoto Ueno
- Division of Morphogenesis, National Institute for Basic BiologyNational Institutes of Natural SciencesAichiJapan
- Basic Biology Programthe Graduate University of Advanced StudiesAichiJapan
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4
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Davidson LA. Gears of life: A primer on the simple machines that shape the embryo. Curr Top Dev Biol 2024; 160:87-109. [PMID: 38937032 DOI: 10.1016/bs.ctdb.2024.05.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/29/2024]
Abstract
A simple machine is a basic of device that takes mechanical advantage to apply force. Animals and plants self-assemble through the operation of a wide variety of simple machines. Embryos of different species actuate these simple machines to drive the geometric transformations that convert a disordered mass of cells into organized structures with discrete identities and function. These transformations are intrinsically coupled to sequential and overlapping steps of self-organization and self-assembly. The processes of self-organization have been explored through the molecular composition of cells and tissues and their information networks. By contrast, efforts to understand the simple machines underlying self-assembly must integrate molecular composition with the physical principles of mechanics. This primer is concerned with effort to elucidate the operation of these machines, focusing on the "problem" of morphogenesis. Advances in understanding self-assembly will ultimately connect molecular-, subcellular-, cellular- and meso-scale functions of plants and animals and their ability to interact with larger ecologies and environmental influences.
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Affiliation(s)
- Lance A Davidson
- Department of Bioengineering, Swanson School of Engineering, Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, United States.
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5
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Boutillon A, Banavar SP, Campàs O. Conserved physical mechanisms of cell and tissue elongation. Development 2024; 151:dev202687. [PMID: 38767601 PMCID: PMC11190436 DOI: 10.1242/dev.202687] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/22/2024]
Abstract
Living organisms have the ability to self-shape into complex structures appropriate for their function. The genetic and molecular mechanisms that enable cells to do this have been extensively studied in several model and non-model organisms. In contrast, the physical mechanisms that shape cells and tissues have only recently started to emerge, in part thanks to new quantitative in vivo measurements of the physical quantities guiding morphogenesis. These data, combined with indirect inferences of physical characteristics, are starting to reveal similarities in the physical mechanisms underlying morphogenesis across different organisms. Here, we review how physics contributes to shape cells and tissues in a simple, yet ubiquitous, morphogenetic transformation: elongation. Drawing from observed similarities across species, we propose the existence of conserved physical mechanisms of morphogenesis.
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Affiliation(s)
- Arthur Boutillon
- Cluster of Excellence Physics of Life, TU Dresden, 01062 Dresden, Germany
| | - Samhita P. Banavar
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08540, USA
| | - Otger Campàs
- Cluster of Excellence Physics of Life, TU Dresden, 01062 Dresden, Germany
- Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany
- Center for Systems Biology Dresden, 01307 Dresden, Germany
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6
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Campàs O, Noordstra I, Yap AS. Adherens junctions as molecular regulators of emergent tissue mechanics. Nat Rev Mol Cell Biol 2024; 25:252-269. [PMID: 38093099 DOI: 10.1038/s41580-023-00688-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/08/2023] [Indexed: 03/28/2024]
Abstract
Tissue and organ development during embryogenesis relies on the collective and coordinated action of many cells. Recent studies have revealed that tissue material properties, including transitions between fluid and solid tissue states, are controlled in space and time to shape embryonic structures and regulate cell behaviours. Although the collective cellular flows that sculpt tissues are guided by tissue-level physical changes, these ultimately emerge from cellular-level and subcellular-level molecular mechanisms. Adherens junctions are key subcellular structures, built from clusters of classical cadherin receptors. They mediate physical interactions between cells and connect biochemical signalling to the physical characteristics of cell contacts, hence playing a fundamental role in tissue morphogenesis. In this Review, we take advantage of the results of recent, quantitative measurements of tissue mechanics to relate the molecular and cellular characteristics of adherens junctions, including adhesion strength, tension and dynamics, to the emergent physical state of embryonic tissues. We focus on systems in which cell-cell interactions are the primary contributor to morphogenesis, without significant contribution from cell-matrix interactions. We suggest that emergent tissue mechanics is an important direction for future research, bridging cell biology, developmental biology and mechanobiology to provide a holistic understanding of morphogenesis in health and disease.
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Affiliation(s)
- Otger Campàs
- Cluster of Excellence Physics of Life, TU Dresden, Dresden, Germany.
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany.
- Center for Systems Biology Dresden, Dresden, Germany.
| | - Ivar Noordstra
- Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland, Australia
| | - Alpha S Yap
- Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland, Australia.
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7
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Yang S, Palmquist KH, Nathan L, Pfeifer CR, Schultheiss PJ, Sharma A, Kam LC, Miller PW, Shyer AE, Rodrigues AR. Morphogens enable interacting supracellular phases that generate organ architecture. Science 2023; 382:eadg5579. [PMID: 37995219 DOI: 10.1126/science.adg5579] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Accepted: 09/27/2023] [Indexed: 11/25/2023]
Abstract
During vertebrate organogenesis, increases in morphological complexity are tightly coupled to morphogen expression. In this work, we studied how morphogens influence self-organizing processes at the collective or "supra"-cellular scale in avian skin. We made physical measurements across length scales, which revealed morphogen-enabled material property differences that were amplified at supracellular scales in comparison to cellular scales. At the supracellular scale, we found that fibroblast growth factor (FGF) promoted "solidification" of tissues, whereas bone morphogenetic protein (BMP) promoted fluidity and enhanced mechanical activity. Together, these effects created basement membrane-less compartments within mesenchymal tissue that were mechanically primed to drive avian skin tissue budding. Understanding this multiscale process requires the ability to distinguish between proximal effects of morphogens that occur at the cellular scale and their functional effects, which emerge at the supracellular scale.
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Affiliation(s)
- Sichen Yang
- Laboratory of Morphogenesis, The Rockefeller University, New York, NY 10065, USA
| | - Karl H Palmquist
- Laboratory of Morphogenesis, The Rockefeller University, New York, NY 10065, USA
| | - Levy Nathan
- Laboratory of Morphogenesis, The Rockefeller University, New York, NY 10065, USA
| | - Charlotte R Pfeifer
- Laboratory of Morphogenesis, The Rockefeller University, New York, NY 10065, USA
| | - Paula J Schultheiss
- Department of Biomedical Engineering, Columbia University, New York, NY 10027, USA
- Department of Medicine, Columbia University, New York, NY 10032, USA
| | - Anurag Sharma
- Electron Microscopy Resource Center, The Rockefeller University, New York, NY 10065, USA
| | - Lance C Kam
- Department of Biomedical Engineering, Columbia University, New York, NY 10027, USA
- Department of Medicine, Columbia University, New York, NY 10032, USA
| | - Pearson W Miller
- Center for Computational Biology, Flatiron Institute, New York, NY 10010, USA
| | - Amy E Shyer
- Laboratory of Morphogenesis, The Rockefeller University, New York, NY 10065, USA
| | - Alan R Rodrigues
- Laboratory of Morphogenesis, The Rockefeller University, New York, NY 10065, USA
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8
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Weng S, Devitt CC, Nyaoga BM, Havnen AE, Alvarado J, Wallingford JB. New tools reveal PCP-dependent polarized mechanics in the cortex and cytoplasm of single cells during convergent extension. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.07.566066. [PMID: 37986924 PMCID: PMC10659385 DOI: 10.1101/2023.11.07.566066] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2023]
Abstract
Understanding biomechanics of biological systems is crucial for unraveling complex processes like tissue morphogenesis. However, current methods for studying cellular mechanics in vivo are limited by the need for specialized equipment and often provide limited spatiotemporal resolution. Here we introduce two new techniques, Tension by Transverse Fluctuation (TFlux) and in vivo microrheology, that overcome these limitations. They both offer time-resolved, subcellular biomechanical analysis using only fluorescent reporters and widely available microscopes. Employing these two techniques, we have revealed a planar cell polarity (PCP)-dependent mechanical gradient both in the cell cortex and the cytoplasm of individual cells engaged in convergent extension. Importantly, the non-invasive nature of these methods holds great promise for its application for uncovering subcellular mechanical variations across a wide array of biological contexts. Summary Non-invasive imaging-based techniques providing time-resolved biomechanical analysis at subcellular scales in developing vertebrate embryos.
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9
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Davidson LA. Microsurgical Methods to Make the Keller Sandwich Explant and the Dorsal Isolate. Cold Spring Harb Protoc 2022; 2022:Pdb.prot097386. [PMID: 35577523 PMCID: PMC9989777 DOI: 10.1101/pdb.prot097386] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Abstract
This protocol summarizes preparation of the dorsal marginal zone sandwich explant (a.k.a. the "Keller sandwich") and the dorsal isolate from Xenopus embryos. The Keller sandwich is assembled from two early gastrula stage dorsal marginal zone (DMZ) explants. DMZ explants isolated before involution maintain planar patterning processes and block radial signals that might be exchanged between pre- and postinvolution tissues. DMZ explants isolated later in gastrulation, but subsequently opened and flattened may have both planar and radial patterning. The epithelial margins of DMZ explants in Keller sandwiches heal and basal contacts form between the deep layers of the two DMZ explants. The dorsal isolate is dissected from mid- to late-gastrula stage embryos after involution and archenteron formation. Germ-layer contacts between dorsal endoderm, mesoderm, and ectoderm generated by gastrulation movements are maintained in the dorsal isolate. These two explants can be used to study tissue, cell, and subcellular processes relevant to convergent extension, from patterning to cell behaviors, and their collective biomechanics. Skills needed to dissect the Keller sandwich are greater than those needed to dissect animal cap ectoderm and can be mastered in a few weeks; skills needed to dissect the dorsal isolate are similar to those needed to dissect animal caps and can be learned in a week.
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Affiliation(s)
- Lance A Davidson
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, USA .,Department of Developmental Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, USA.,Department of Computational and Systems Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, USA
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10
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Tracking of Endothelial Cell Migration and Stiffness Measurements Reveal the Role of Cytoskeletal Dynamics. Int J Mol Sci 2022; 23:ijms23010568. [PMID: 35008993 PMCID: PMC8745078 DOI: 10.3390/ijms23010568] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Revised: 12/23/2021] [Accepted: 12/30/2021] [Indexed: 02/01/2023] Open
Abstract
Cell migration is a complex, tightly regulated multistep process in which cytoskeletal reorganization and focal adhesion redistribution play a central role. Core to both individual and collective migration is the persistent random walk, which is characterized by random force generation and resistance to directional change. We first discuss a model that describes the stochastic movement of ECs and characterizes EC persistence in wound healing. To that end, we pharmacologically disrupted cytoskeletal dynamics, cytochalasin D for actin and nocodazole for tubulin, to understand its contributions to cell morphology, stiffness, and motility. As such, the use of Atomic Force Microscopy (AFM) enabled us to probe the topography and stiffness of ECs, while time lapse microscopy provided observations in wound healing models. Our results suggest that actin and tubulin dynamics contribute to EC shape, compressive moduli, and directional organization in collective migration. Insights from the model and time lapse experiment suggest that EC speed and persistence are directionally organized in wound healing. Pharmacological disruptions suggest that actin and tubulin dynamics play a role in collective migration. Current insights from both the model and experiment represent an important step in understanding the biomechanics of EC migration as a therapeutic target.
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11
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Mechanics of neural tube morphogenesis. Semin Cell Dev Biol 2021; 130:56-69. [PMID: 34561169 DOI: 10.1016/j.semcdb.2021.09.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Revised: 09/07/2021] [Accepted: 09/10/2021] [Indexed: 01/07/2023]
Abstract
The neural tube is an important model system of morphogenesis representing the developmental module of out-of-plane epithelial deformation. As the embryonic precursor of the central nervous system, the neural tube also holds keys to many defects and diseases. Recent advances begin to reveal how genetic, cellular and environmental mechanisms work in concert to ensure correct neural tube shape. A physical model is emerging where these factors converge at the regulation of the mechanical forces and properties within and around the tissue that drive tube formation towards completion. Here we review the dynamics and mechanics of neural tube morphogenesis and discuss the underlying cellular behaviours from the viewpoint of tissue mechanics. We will also highlight some of the conceptual and technical next steps.
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12
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Furry is required for cell movements during gastrulation and functionally interacts with NDR1. Sci Rep 2021; 11:6607. [PMID: 33758327 PMCID: PMC7987989 DOI: 10.1038/s41598-021-86153-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Accepted: 03/11/2021] [Indexed: 11/09/2022] Open
Abstract
Gastrulation is a key event in animal embryogenesis during which germ layer precursors are rearranged and the embryonic axes are established. Cell polarization is essential during gastrulation, driving asymmetric cell division, cell movements, and cell shape changes. The furry (fry) gene encodes an evolutionarily conserved protein with a wide variety of cellular functions, including cell polarization and morphogenesis in invertebrates. However, little is known about its function in vertebrate development. Here, we show that in Xenopus, Fry plays a role in morphogenetic processes during gastrulation, in addition to its previously described function in the regulation of dorsal mesoderm gene expression. Using morpholino knock-down, we demonstrate a distinct role for Fry in blastopore closure and dorsal axis elongation. Loss of Fry function drastically affects the movement and morphological polarization of cells during gastrulation and disrupts dorsal mesoderm convergent extension, responsible for head-to-tail elongation. Finally, we evaluate a functional interaction between Fry and NDR1 kinase, providing evidence of an evolutionarily conserved complex required for morphogenesis.
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13
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Lee H, Bonin K, Guthold M. Human mammary epithelial cells in a mature, stratified epithelial layer flatten and stiffen compared to single and confluent cells. Biochim Biophys Acta Gen Subj 2021; 1865:129891. [PMID: 33689830 DOI: 10.1016/j.bbagen.2021.129891] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Revised: 02/07/2021] [Accepted: 03/03/2021] [Indexed: 10/22/2022]
Abstract
BACKGROUND The epithelium forms a protective barrier against external biological, chemical and physical insults. So far, AFM-based, micro-mechanical measurements have only been performed on single cells and confluent cells, but not yet on cells in mature layers. METHODS Using a combination of atomic force, fluorescence and confocal microscopy, we determined the changes in stiffness, morphology and actin distribution of human mammary epithelial cells (HMECs) as they transition from single cells to confluency to a mature layer. RESULTS Single HMECs have a tall, round (planoconvex) morphology, have actin stress fibers at the base, have diffuse cortical actin, and have a stiffness of 1 kPa. Confluent HMECs start to become flatter, basal actin stress fibers start to disappear, and actin accumulates laterally where cells abut. Overall stiffness is still 1 kPa with two-fold higher stiffness in the abutting regions. As HMECs mature and form multilayered structures, cells on apical surfaces become flatter (apically more level), wider, and seven times stiffer (mean, 7 kPa) than single and confluent cells. The main drivers of these changes are actin filaments, as cells show strong actin accumulation in the regions where cells adjoin, and in the apical regions. CONCLUSIONS HMECs stiffen, flatten and redistribute actin upon transiting from single cells to mature, confluent layers. GENERAL SIGNIFICANCE Our findings advance the understanding of breast ductal morphogenesis and mechanical homeostasis.
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Affiliation(s)
- Hyunsu Lee
- Department of Physics, Wake Forest University, Winston-Salem, NC 27109, USA
| | - Keith Bonin
- Department of Physics, Wake Forest University, Winston-Salem, NC 27109, USA
| | - Martin Guthold
- Department of Physics, Wake Forest University, Winston-Salem, NC 27109, USA.
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14
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Tissue mechanics drives regeneration of a mucociliated epidermis on the surface of Xenopus embryonic aggregates. Nat Commun 2020; 11:665. [PMID: 32005801 PMCID: PMC6994656 DOI: 10.1038/s41467-020-14385-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Accepted: 12/09/2019] [Indexed: 12/20/2022] Open
Abstract
Injury, surgery, and disease often disrupt tissues and it is the process of regeneration that aids the restoration of architecture and function. Regeneration can occur through multiple strategies including stem cell expansion, transdifferentiation, or proliferation of differentiated cells. We have identified a case of regeneration in Xenopus embryonic aggregates that restores a mucociliated epithelium from mesenchymal cells. Following disruption of embryonic tissue architecture and assembly of a compact mesenchymal aggregate, regeneration first restores an epithelium, transitioning from mesenchymal cells at the surface of the aggregate. Cells establish apico-basal polarity within 5 hours and a mucociliated epithelium within 24 hours. Regeneration coincides with nuclear translocation of the putative mechanotransducer YAP1 and a sharp increase in aggregate stiffness, and regeneration can be controlled by altering stiffness. We propose that regeneration of a mucociliated epithelium occurs in response to biophysical cues sensed by newly exposed cells on the surface of a disrupted mesenchymal tissue.
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15
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Weber A, Iturri J, Benitez R, Zemljic-Jokhadar S, Toca-Herrera JL. Microtubule disruption changes endothelial cell mechanics and adhesion. Sci Rep 2019; 9:14903. [PMID: 31624281 PMCID: PMC6797797 DOI: 10.1038/s41598-019-51024-z] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2019] [Accepted: 09/24/2019] [Indexed: 12/27/2022] Open
Abstract
The interest in studying the mechanical and adhesive properties of cells has increased in recent years. The cytoskeleton is known to play a key role in cell mechanics. However, the role of the microtubules in shaping cell mechanics is not yet well understood. We have employed Atomic Force Microscopy (AFM) together with confocal fluorescence microscopy to determine the role of microtubules in cytomechanics of Human Umbilical Vein Endothelial Cells (HUVECs). Additionally, the time variation of the adhesion between tip and cell surface was studied. The disruption of microtubules by exposing the cells to two colchicine concentrations was monitored as a function of time. Already, after 30 min of incubation the cells stiffened, their relaxation times increased (lower fluidity) and the adhesion between tip and cell decreased. This was accompanied by cytoskeletal rearrangements, a reduction in cell area and changes in cell shape. Over the whole experimental time, different behavior for the two used concentrations was found while for the control the values remained stable. This study underlines the role of microtubules in shaping endothelial cell mechanics.
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Affiliation(s)
- Andreas Weber
- Institute for Biophysics, Department of Nanobiotechnology, University of Natural Resources and Life Sciences Vienna, Muthgasse 11, A-1190, Vienna, Austria.
| | - Jagoba Iturri
- Institute for Biophysics, Department of Nanobiotechnology, University of Natural Resources and Life Sciences Vienna, Muthgasse 11, A-1190, Vienna, Austria
| | - Rafael Benitez
- Dpto. Matemáticas para la Economía y la Empresa, Facultad de Economía, Universidad de Valencia, Avda. Tarongers s/n, 46022, Valencia, Spain
| | - Spela Zemljic-Jokhadar
- Department of Biophysics, Medicine Faculty, University of Ljubljana, Vrazov trg 2, 1000, Ljubljana, Slovenia
| | - José L Toca-Herrera
- Institute for Biophysics, Department of Nanobiotechnology, University of Natural Resources and Life Sciences Vienna, Muthgasse 11, A-1190, Vienna, Austria.
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16
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Mongera A, Michaut A, Guillot C, Xiong F, Pourquié O. Mechanics of Anteroposterior Axis Formation in Vertebrates. Annu Rev Cell Dev Biol 2019; 35:259-283. [PMID: 31412208 PMCID: PMC7394480 DOI: 10.1146/annurev-cellbio-100818-125436] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The vertebrate anteroposterior axis forms through elongation of multiple tissues during embryogenesis. This process is based on tissue-autonomous mechanisms of force generation and intertissue mechanical coupling whose failure leads to severe developmental anomalies such as body truncation and spina bifida. Similar to other morphogenetic modules, anteroposterior body extension requires both the rearrangement of existing materials-such as cells and extracellular matrix-and the local addition of new materials, i.e., anisotropic growth, through cell proliferation, cell growth, and matrix deposition. Numerous signaling pathways coordinate body axis formation via regulation of cell behavior during tissue rearrangements and/or volumetric growth. From a physical perspective, morphogenesis depends on both cell-generated forces and tissue material properties. As the spatiotemporal variation of these mechanical parameters has recently been explored in the context of vertebrate body elongation, the study of this process is likely to shed light on the cross talk between signaling and mechanics during morphogenesis.
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Affiliation(s)
- Alessandro Mongera
- Department of Genetics, Harvard Medical School, and Department of Pathology, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA;
| | - Arthur Michaut
- Department of Genetics, Harvard Medical School, and Department of Pathology, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA;
| | - Charlène Guillot
- Department of Genetics, Harvard Medical School, and Department of Pathology, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA;
| | - Fengzhu Xiong
- Department of Genetics, Harvard Medical School, and Department of Pathology, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA;
| | - Olivier Pourquié
- Department of Genetics, Harvard Medical School, and Department of Pathology, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA;
- Harvard Stem Cell Institute, Harvard University, Cambridge, Massachusetts 02138, USA
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17
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Shawky JH, Balakrishnan UL, Stuckenholz C, Davidson LA. Multiscale analysis of architecture, cell size and the cell cortex reveals cortical F-actin density and composition are major contributors to mechanical properties during convergent extension. Development 2018; 145:dev161281. [PMID: 30190279 PMCID: PMC6198471 DOI: 10.1242/dev.161281] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Accepted: 08/31/2018] [Indexed: 12/20/2022]
Abstract
The large-scale movements that construct complex three-dimensional tissues during development are governed by universal physical principles. Fine-grained control of both mechanical properties and force production is crucial to the successful placement of tissues and shaping of organs. Embryos of the frog Xenopus laevis provide a dramatic example of these physical processes, as dorsal tissues increase in Young's modulus by six-fold to 80 Pascal over 8 h as germ layers and the central nervous system are formed. These physical changes coincide with emergence of complex anatomical structures, rounds of cell division, and cytoskeletal remodeling. To understand the contribution of these diverse structures, we adopt the cellular solids model to relate bulk stiffness of a solid foam to the unit size of individual cells, their microstructural organization, and their material properties. Our results indicate that large-scale tissue architecture and cell size are not likely to influence the bulk mechanical properties of early embryonic or progenitor tissues but that F-actin cortical density and composition of the F-actin cortex play major roles in regulating the physical mechanics of embryonic multicellular tissues.
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Affiliation(s)
- Joseph H Shawky
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Uma L Balakrishnan
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Carsten Stuckenholz
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Lance A Davidson
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15213, USA
- Department of Computational and Systems Biology, University of Pittsburgh, Pittsburgh, PA 15213, USA
- Department of Developmental Biology, University of Pittsburgh, Pittsburgh, PA 15213, USA
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18
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Emergent mechanics of actomyosin drive punctuated contractions and shape network morphology in the cell cortex. PLoS Comput Biol 2018; 14:e1006344. [PMID: 30222728 PMCID: PMC6171965 DOI: 10.1371/journal.pcbi.1006344] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Revised: 10/04/2018] [Accepted: 07/05/2018] [Indexed: 11/24/2022] Open
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. 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 organs. In this paper we developed computer simulations of these scaffolds, composed of filamentous actin (F-actin), a rod-like protein polymer, and mini-thick filaments, composed of non-muscle myosin II, forming a two headed spring-like complex of motor proteins that can walk on, and remodel F-actin networks. Using simulations of these dynamic interactions, we can carry out virtual experiments where we change the physics and chemistry of F-actin polymers, their associated myosin motors, and cross-linkers and observe the changes in scaffolds that emerge. For example, by modulating the motor stiffness of the myosin motors in our model we can observe the formation or loss of large aster-like structures. Such fine-grained control over the physical properties of motors or filaments within simulations are not currently possible with biological experiments, even where mutant proteins or small molecule inhibitors can be targeted to specific sites on filaments or motors. Our approach reflects a growing adoption of simulation methods to investigate microscopic features that shape actomyosin arrays and the mesoscale effects of molecular scale processes. We expect predictions from these models will drive more refined experimental approaches to expose the many roles of actomyosin in development.
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19
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Shook DR, Kasprowicz EM, Davidson LA, Keller R. Large, long range tensile forces drive convergence during Xenopus blastopore closure and body axis elongation. eLife 2018; 7:e26944. [PMID: 29533180 PMCID: PMC5896886 DOI: 10.7554/elife.26944] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Accepted: 03/12/2018] [Indexed: 02/03/2023] Open
Abstract
Indirect evidence suggests that blastopore closure during gastrulation of anamniotes, including amphibians such as Xenopus laevis, depends on circumblastoporal convergence forces generated by the marginal zone (MZ), but direct evidence is lacking. We show that explanted MZs generate tensile convergence forces up to 1.5 μN during gastrulation and over 4 μN thereafter. These forces are generated by convergent thickening (CT) until the midgastrula and increasingly by convergent extension (CE) thereafter. Explants from ventralized embryos, which lack tissues expressing CE but close their blastopores, produce up to 2 μN of tensile force, showing that CT alone generates forces sufficient to close the blastopore. Uniaxial tensile stress relaxation assays show stiffening of mesodermal and ectodermal tissues around the onset of neurulation, potentially enhancing long-range transmission of convergence forces. These results illuminate the mechanobiology of early vertebrate morphogenic mechanisms, aid interpretation of phenotypes, and give insight into the evolution of blastopore closure mechanisms.
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Affiliation(s)
- David R Shook
- Department of BiologyUniversity of VirginiaCharlottesvilleUnited States
| | - Eric M Kasprowicz
- Department of Internal MedicineThomas Jefferson University HospitalPhiladelphiaUnited States
| | - Lance A Davidson
- Department of Computational and Systems BiologyUniversity of PittsburghPittsburghUnited States
- Department of BioengineeringUniversity of PittsburghPittsburghUnited States
| | - Raymond Keller
- Department of BiologyUniversity of VirginiaCharlottesvilleUnited States
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20
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Linde-Medina M, Marcucio R. Living tissues are more than cell clusters: The extracellular matrix as a driving force in morphogenesis. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2018; 137:46-51. [PMID: 29398066 DOI: 10.1016/j.pbiomolbio.2018.01.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2017] [Revised: 01/18/2018] [Accepted: 01/23/2018] [Indexed: 12/24/2022]
Abstract
In the study of morphogenesis, there is a general tendency to look at the extracellular matrix (ECM) as a mechanically passive agent that simply gives support to cells, and consequently, to place all the explanatory burden on cellular behaviors. Here we aimed to show that not only cells, but also the ECM may be an important force of morphogenesis. Understanding the mechanical role of the ECM broadens our view of morphogenesis and stresses the importance of considering embryonic tissues as a composite of cells and ECM.
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Affiliation(s)
- Marta Linde-Medina
- Department of Orthopaedic Surgery, San Francisco General Hospital, Orthopaedic Trauma Institute, University of California, San Francisco, CA 94110, USA.
| | - Ralph Marcucio
- Department of Orthopaedic Surgery, San Francisco General Hospital, Orthopaedic Trauma Institute, University of California, San Francisco, CA 94110, USA
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21
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Logan CM, Bowen CJ, Menko AS. Functional role for stable microtubules in lens fiber cell elongation. Exp Cell Res 2017; 362:477-488. [PMID: 29253534 DOI: 10.1016/j.yexcr.2017.12.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Revised: 11/17/2017] [Accepted: 12/13/2017] [Indexed: 02/06/2023]
Abstract
The process of tissue morphogenesis, especially for tissues reliant on the establishment of a specific cytoarchitecture for their functionality, depends a balanced interplay between cytoskeletal elements and their interactions with cell adhesion molecules. The microtubule cytoskeleton, which has many roles in the cell, is a determinant of directional cell migration, a process that underlies many aspects of development. We investigated the role of microtubules in development of the lens, a tissue where cell elongation underlies morphogenesis. Our studies with the microtubule depolymerizing agent nocodazole revealed an essential function for the acetylated population of stable microtubules in the elongation of lens fiber cells, which was linked to their regulation of the activation state of myosin. Suppressing myosin activation with the inhibitor blebbistatin could attenuate the loss of acetylated microtubules by nocodazole and rescue the effect of this microtubule depolymerization agent on both fiber cell elongation and lens integrity. Our results also suggest that acetylated microtubules impact lens morphogenesis through their interaction with N-cadherin junctions, with which they specifically associate in the region where lens fiber cell elongate. Disruption of the stable microtubule network increased N-cadherin junctional organization along lateral borders of differentiating lens fiber cells, which was prevented by suppression of myosin activity. These results reveal a role for the stable microtubule population in lens fiber cell elongation, acting in tandem with N-cadherin cell-cell junctions and the actomyosin network, giving insight into the cooperative role these systems play in tissue morphogenesis.
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Affiliation(s)
- Caitlin M Logan
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107, United States.
| | - Caitlin J Bowen
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107, United States.
| | - A Sue Menko
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107, United States.
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22
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Dureau M, Alessandri A, Bagnerini P, Vincent S. Modeling and Identification of Amnioserosa Cell Mechanical Behavior by Using Mass-Spring Lattices. IEEE/ACM TRANSACTIONS ON COMPUTATIONAL BIOLOGY AND BIOINFORMATICS 2017; 14:1476-1481. [PMID: 27362988 DOI: 10.1109/tcbb.2016.2586063] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Various mechanical models of live amnioserosa cells during Drosophila melanogaster's dorsal closure are proposed. Such models account for specific biomechanical oscillating behaviors and depend on a different set of parameters. The identification of the parameters for each of the proposed models is accomplished according to a least-squares approach in such a way to best fit the cellular dynamics extracted from live images. For the purpose of comparison, the resulting models after identification are validated to allow for the selection of the most appropriate description of such a cell dynamics. The proposed methodology is general and it may be applied to other planar biological processes.
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23
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An engineering insight into the relationship of selective cytoskeletal impairment and biomechanics of HeLa cells. Micron 2017; 102:88-96. [DOI: 10.1016/j.micron.2017.09.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Revised: 08/22/2017] [Accepted: 09/04/2017] [Indexed: 10/24/2022]
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24
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Das D, Chatti V, Emonet T, Holley SA. Patterned Disordered Cell Motion Ensures Vertebral Column Symmetry. Dev Cell 2017; 42:170-180.e5. [PMID: 28743003 DOI: 10.1016/j.devcel.2017.06.020] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2016] [Revised: 03/30/2017] [Accepted: 06/23/2017] [Indexed: 12/24/2022]
Abstract
The biomechanics of posterior embryonic growth must be dynamically regulated to ensure bilateral symmetry of the spinal column. Throughout vertebrate trunk elongation, motile mesodermal progenitors undergo an order-to-disorder transition via an epithelial-to-mesenchymal transition and sort symmetrically into the left and right paraxial mesoderm. We combine theoretical modeling of cell migration in a tail-bud-like geometry with experimental data analysis to assess the importance of ordered and disordered cell motion. We find that increasing order in cell motion causes a phase transition from symmetric to asymmetric body elongation. In silico and in vivo, overly ordered cell motion converts normal anisotropic fluxes into stable vortices near the posterior tail bud, contributing to asymmetric cell sorting. Thus, disorder is a physical mechanism that ensures the bilateral symmetry of the spinal column. These physical properties of the tissue connect across scales such that patterned disorder at the cellular level leads to the emergence of organism-level order.
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Affiliation(s)
- Dipjyoti Das
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT, USA
| | - Veena Chatti
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT, USA
| | - Thierry Emonet
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT, USA; Department of Physics, Yale University, New Haven, CT, USA.
| | - Scott A Holley
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT, USA.
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25
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Athamneh AIM, He Y, Lamoureux P, Fix L, Suter DM, Miller KE. Neurite elongation is highly correlated with bulk forward translocation of microtubules. Sci Rep 2017; 7:7292. [PMID: 28779177 PMCID: PMC5544698 DOI: 10.1038/s41598-017-07402-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Accepted: 06/28/2017] [Indexed: 11/09/2022] Open
Abstract
During the development of the nervous system and regeneration following injury, microtubules (MTs) are required for neurite elongation. Whether this elongation occurs primarily through tubulin assembly at the tip of the axon, the transport of individual MTs, or because MTs translocate forward in bulk is unclear. Using fluorescent speckle microscopy (FSM), differential interference contrast (DIC), and phase contrast microscopy, we tracked the movement of MTs, phase dense material, and docked mitochondria in chick sensory and Aplysia bag cell neurons growing rapidly on physiological substrates. In all cases, we find that MTs and other neuritic components move forward in bulk at a rate that on average matches the velocity of neurite elongation. To better understand whether and why MT assembly is required for bulk translocation, we disrupted it with nocodazole. We found this blocked the forward bulk advance of material along the neurite and was paired with a transient increase in axonal tension. This indicates that disruption of MT dynamics interferes with neurite outgrowth, not by disrupting the net assembly of MTs at the growth cone, but rather because it alters the balance of forces that power the bulk forward translocation of MTs.
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Affiliation(s)
- Ahmad I M Athamneh
- Department of Biological Sciences, Purdue University, West Lafayette, IN, 47907, USA
| | - Yingpei He
- Department of Biological Sciences, Purdue University, West Lafayette, IN, 47907, USA
| | - Phillip Lamoureux
- Department of Integrative Biology, Michigan State University, East Lansing, MI, 48824, USA
| | - Lucas Fix
- Department of Integrative Biology, Michigan State University, East Lansing, MI, 48824, USA
| | - Daniel M Suter
- Department of Biological Sciences, Purdue University, West Lafayette, IN, 47907, USA. .,Purdue Institute for Integrative Neuroscience, Purdue University, West Lafayette, IN, 47907, USA. .,Bindley Bioscience Center, Purdue University, West Lafayette, IN, 47907, USA. .,Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA.
| | - Kyle E Miller
- Department of Integrative Biology, Michigan State University, East Lansing, MI, 48824, USA.
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26
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Jackson TR, Kim HY, Balakrishnan UL, Stuckenholz C, Davidson LA. Spatiotemporally Controlled Mechanical Cues Drive Progenitor Mesenchymal-to-Epithelial Transition Enabling Proper Heart Formation and Function. Curr Biol 2017; 27:1326-1335. [PMID: 28434863 DOI: 10.1016/j.cub.2017.03.065] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Revised: 02/14/2017] [Accepted: 03/27/2017] [Indexed: 10/19/2022]
Abstract
During early cardiogenesis, bilateral fields of mesenchymal heart progenitor cells (HPCs) move from the anterior lateral plate mesoderm to the ventral midline, undergoing a mesenchymal-to-epithelial transition (MET) en route to forming a single epithelial sheet. Through tracking of tissue-level deformations in the heart-forming region (HFR) as well as movement trajectories and traction generation of individual HPCs, we find that the onset of MET correlates with a peak in mechanical stress within the HFR and changes in HPC migratory behaviors. Small-molecule inhibitors targeting actomyosin contractility reveal a temporally specific requirement of bulk tissue compliance to regulate heart development and MET. Targeting mutant constructs to modulate contractility and compliance in the underlying endoderm, we find that MET in HPCs can be accelerated in response to microenvironmental stiffening and can be inhibited by softening. To test whether MET in HPCs was responsive to purely physical mechanical cues, we mimicked a high-stress state by injecting an inert oil droplet to generate high strain in the HFR, demonstrating that exogenously applied stress was sufficient to drive MET. MET-induced defects in anatomy result in defined functional lesions in the larval heart, implicating mechanical signaling and MET in the etiology of congenital heart defects. From this integrated analysis of HPC polarity and mechanics, we propose that normal heart development requires bilateral HPCs to undergo a critical behavioral and phenotypic transition on their way to the ventral midline, and that this transition is driven in response to the changing mechanical properties of their endoderm substrate.
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Affiliation(s)
- Timothy R Jackson
- Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Hye Young Kim
- Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Uma L Balakrishnan
- Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Carsten Stuckenholz
- Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Lance A Davidson
- Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA 15213, USA; Department of Developmental Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15260, USA; Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15260, USA.
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27
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D. S. V, L. A. D. Mechanics of neurulation: From classical to current perspectives on the physical mechanics that shape, fold, and form the neural tube. Birth Defects Res 2017; 109:153-168. [PMID: 27620928 PMCID: PMC9972508 DOI: 10.1002/bdra.23557] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Neural tube defects arise from mechanical failures in the process of neurulation. At the most fundamental level, formation of the neural tube relies on coordinated, complex tissue movements that mechanically transform the flat neural epithelium into a lumenized epithelial tube (Davidson, 2012). The nature of this mechanical transformation has mystified embryologists, geneticists, and clinicians for more than 100 years. Early embryologists pondered the physical mechanisms that guide this transformation. Detailed observations of cell and tissue movements as well as experimental embryological manipulations allowed researchers to generate and test elementary hypotheses of the intrinsic and extrinsic forces acting on the neural tissue. Current research has turned toward understanding the molecular mechanisms underlying neurulation. Genetic and molecular perturbation have identified a multitude of subcellular components that correlate with cell behaviors and tissue movements during neural tube formation. In this review, we focus on methods and conceptual frameworks that have been applied to the study of amphibian neurulation that can be used to determine how molecular and physical mechanisms are integrated and responsible for neurulation. We will describe how qualitative descriptions and quantitative measurements of strain, force generation, and tissue material properties as well as simulations can be used to understand how embryos use morphogenetic programs to drive neurulation. Birth Defects Research 109:153-168, 2017. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Vijayraghavan D. S.
- Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA 15260
| | - Davidson L. A.
- Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA 15260,Department of Developmental Biology, School of Medicine, University of Pittsburgh Pittsburgh, PA 15213,Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15260
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28
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Khalilgharibi N, Fouchard J, Recho P, Charras G, Kabla A. The dynamic mechanical properties of cellularised aggregates. Curr Opin Cell Biol 2016; 42:113-120. [PMID: 27371889 DOI: 10.1016/j.ceb.2016.06.003] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2016] [Revised: 06/14/2016] [Accepted: 06/16/2016] [Indexed: 01/13/2023]
Abstract
Cellularised materials are composed of cells interfaced through specialised intercellular junctions that link the cytoskeleton of one cell to that of its neighbours allowing for transmission of forces. Cellularised materials are common in early development and adult tissues where they can be found in the form of cell sheets, cysts, or amorphous aggregates and in pathophysiological conditions such as cancerous tumours. Given the growing realisation that forces can regulate cell physiology and developmental processes, understanding how cellularised materials deform under mechanical stress or dissipate stress appear as key biological questions. In this review, we will discuss the dynamic mechanical properties of cellularised materials devoid of extracellular matrix.
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Affiliation(s)
- Nargess Khalilgharibi
- London Centre for Nanotechnology, University College London, UK; CoMPLEX PhD Program, University College London, UK
| | | | - Pierre Recho
- Department of Mechanical Engineering, Cambridge University, UK
| | - Guillaume Charras
- London Centre for Nanotechnology, University College London, UK; Department of Cell and Developmental Biology, University College London, UK; Institute for the Physics of Living Systems, University College London, UK.
| | - Alexandre Kabla
- Department of Mechanical Engineering, Cambridge University, UK.
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29
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Kim HY, Jackson TR, Davidson LA. On the role of mechanics in driving mesenchymal-to-epithelial transitions. Semin Cell Dev Biol 2016; 67:113-122. [PMID: 27208723 DOI: 10.1016/j.semcdb.2016.05.011] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Revised: 05/12/2016] [Accepted: 05/17/2016] [Indexed: 01/27/2023]
Abstract
The mesenchymal-to-epithelial transition (MET) is an intrinsically mechanical process describing a multi-step progression where autonomous mesenchymal cells gradually become tightly linked, polarized epithelial cells. METs are fundamental to a wide range of biological processes, including the evolution of multicellular organisms, generation of primary and secondary epithelia during development and organogenesis, and the progression of diseases including cancer. In these cases, there is an interplay between the establishment of cell polarity and the mechanics of neighboring cells and microenvironment. In this review, we highlight a spectrum of METs found in normal development as well as in pathological lesions, and provide insight into the critical role mechanics play at each step. We define MET as an independent process, distinct from a reverse-EMT, and propose questions to further explore the cellular and physical mechanisms of MET.
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Affiliation(s)
- Hye Young Kim
- Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Timothy R Jackson
- Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Lance A Davidson
- Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA 15213, USA; Department of Developmental Biology, University of Pittsburgh School of Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA; Department of Computational and Systems Biology, University of Pittsburgh School of Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA.
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30
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Schiele NR, von Flotow F, Tochka ZL, Hockaday LA, Marturano JE, Thibodeau JJ, Kuo CK. Actin cytoskeleton contributes to the elastic modulus of embryonic tendon during early development. J Orthop Res 2015; 33:874-81. [PMID: 25721681 PMCID: PMC4889338 DOI: 10.1002/jor.22880] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/06/2014] [Accepted: 02/20/2015] [Indexed: 02/04/2023]
Abstract
Tendon injuries are common and heal poorly. Strategies to regenerate or replace injured tendons are challenged by an incomplete understanding of normal tendon development. Our previous study showed that embryonic tendon elastic modulus increases as a function of developmental stage. Inhibition of enzymatic collagen crosslink formation abrogated increases in tendon elastic modulus at late developmental stages, but did not affect increases in elastic modulus of early stage embryonic tendons. Here, we aimed to identify potential contributors to the mechanical properties of these early stage embryonic tendons. We characterized tendon progenitor cells in early stage embryonic tendons, and the influence of actin cytoskeleton disruption on tissue elastic modulus. Cells were closely packed in embryonic tendons, and did not change in density during early development. We observed an organized network of actin filaments that seemed contiguous between adjacent cells. The actin filaments exhibited a crimp pattern with a period and amplitude that matched the crimp of collagen fibers at each developmental stage. Chemical disruption of the actin cytoskeleton decreased tendon tissue elastic modulus, measured by atomic force microscopy. Our results demonstrate that early developmental stage embryonic tendons possess a well organized actin cytoskeleton network that contributes significantly to tendon tissue mechanical properties.
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Affiliation(s)
- Nathan R. Schiele
- Department of Biomedical Engineering, Tufts University, Medford, Massachusetts
| | | | - Zachary L. Tochka
- Department of Biomedical Engineering, Tufts University, Medford, Massachusetts
| | - Laura A. Hockaday
- Department of Biomedical Engineering, Tufts University, Medford, Massachusetts
| | - Joseph E. Marturano
- Department of Biomedical Engineering, Tufts University, Medford, Massachusetts
| | | | - Catherine K. Kuo
- Department of Biomedical Engineering, Tufts University, Medford, Massachusetts,Cell, Molecular & Developmental Biology Program, Sackler School of Graduate Biomedical Sciences, Tufts University School of Medicine, Boston, Massachusetts
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31
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Lee H, Adams WJ, Alford PW, McCain ML, Feinberg AW, Sheehy SP, Goss JA, Parker KK. Cytoskeletal prestress regulates nuclear shape and stiffness in cardiac myocytes. Exp Biol Med (Maywood) 2015; 240:1543-54. [PMID: 25908635 DOI: 10.1177/1535370215583799] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Accepted: 02/27/2015] [Indexed: 12/22/2022] Open
Abstract
Mechanical stresses on the myocyte nucleus have been associated with several diseases and potentially transduce mechanical stimuli into cellular responses. Although a number of physical links between the nuclear envelope and cytoplasmic filaments have been identified, previous studies have focused on the mechanical properties of individual components of the nucleus, such as the nuclear envelope and lamin network. The mechanical interaction between the cytoskeleton and chromatin on nuclear deformability remains elusive. Here, we investigated how cytoskeletal and chromatin structures influence nuclear mechanics in cardiac myocytes. Rapid decondensation of chromatin and rupture of the nuclear membrane caused a sudden expansion of DNA, a consequence of prestress exerted on the nucleus. To characterize the prestress exerted on the nucleus, we measured the shape and the stiffness of isolated nuclei and nuclei in living myocytes during disruption of cytoskeletal, myofibrillar, and chromatin structure. We found that the nucleus in myocytes is subject to both tensional and compressional prestress and its deformability is determined by a balance of those opposing forces. By developing a computational model of the prestressed nucleus, we showed that cytoskeletal and chromatin prestresses create vulnerability in the nuclear envelope. Our studies suggest the cytoskeletal-nuclear-chromatin interconnectivity may play an important role in mechanics of myocyte contraction and in the development of laminopathies by lamin mutations.
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Affiliation(s)
- Hyungsuk Lee
- Disease Biophysics Group, Wyss Institute for Biologically Inspired Engineering, School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA School of Mechanical Engineering, Yonsei University, Seoul 120-749, Korea
| | - William J Adams
- Disease Biophysics Group, Wyss Institute for Biologically Inspired Engineering, School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
| | - Patrick W Alford
- Disease Biophysics Group, Wyss Institute for Biologically Inspired Engineering, School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA Department of Biomedical Engineering, University of Minnesota-Twin Cities, Minneapolis, MN 55455, USA
| | - Megan L McCain
- Disease Biophysics Group, Wyss Institute for Biologically Inspired Engineering, School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA Department of Biomedical Engineering, Department of Stem Cell Biology and Regenerative Medicine, University of Southern California, Los Angeles, CA 90089, USA
| | - Adam W Feinberg
- Disease Biophysics Group, Wyss Institute for Biologically Inspired Engineering, School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA Department of Materials Science and Engineering, Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA 15219, USA
| | - Sean P Sheehy
- Disease Biophysics Group, Wyss Institute for Biologically Inspired Engineering, School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
| | - Josue A Goss
- Disease Biophysics Group, Wyss Institute for Biologically Inspired Engineering, School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
| | - Kevin Kit Parker
- Disease Biophysics Group, Wyss Institute for Biologically Inspired Engineering, School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
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McMillen P, Holley SA. The tissue mechanics of vertebrate body elongation and segmentation. Curr Opin Genet Dev 2015; 32:106-11. [PMID: 25796079 DOI: 10.1016/j.gde.2015.02.005] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Revised: 02/05/2015] [Accepted: 02/07/2015] [Indexed: 10/23/2022]
Abstract
England's King Richard III, whose skeleton was recently discovered lying ignobly beneath a parking lot, suffered from a lateral curvature of his spinal column called scoliosis. We now know that his scoliosis was not caused by 'imbalanced bodily humors', rather vertebral defects arise from defects in embryonic elongation and segmentation. This review highlights recent advances in our understanding of post-gastrulation biomechanics of the posteriorly advancing tailbud and somite morphogenesis. These processes are beginning to be deciphered from the level of gene networks to a cross-scale physical model incorporating cellular mechanics, the extracellular matrix, and tissue fluidity.
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Affiliation(s)
- Patrick McMillen
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520, United States
| | - Scott A Holley
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520, United States.
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33
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On human pluripotent stem cell control: The rise of 3D bioengineering and mechanobiology. Biomaterials 2015; 52:26-43. [PMID: 25818411 DOI: 10.1016/j.biomaterials.2015.01.078] [Citation(s) in RCA: 81] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Revised: 12/24/2014] [Accepted: 01/28/2015] [Indexed: 12/11/2022]
Abstract
Human pluripotent stem cells (hPSCs) provide promising resources for regenerating tissues and organs and modeling development and diseases in vitro. To fulfill their promise, the fate, function, and organization of hPSCs need to be precisely regulated in a three-dimensional (3D) environment to mimic cellular structures and functions of native tissues and organs. In the past decade, innovations in 3D culture systems with functional biomaterials have enabled efficient and versatile control of hPSC fate at the cellular level. However, we are just at the beginning of bringing hPSC-based regeneration and development and disease modeling to the tissue and organ levels. In this review, we summarize existing bioengineered culture platforms for controlling hPSC fate and function by regulating inductive mechanical and biochemical cues coexisting in the synthetic cell microenvironment. We highlight recent excitements in developing 3D hPSC-based in vitro tissue and organ models with in vivo-like cellular structures, interactions, and functions. We further discuss an emerging multifaceted mechanotransductive signaling network--with transcriptional coactivators YAP and TAZ at the center stage--that regulate fates and behaviors of mammalian cells, including hPSCs. Future development of 3D biomaterial systems should incorporate dynamically modulated mechanical and chemical properties targeting specific intracellular signaling events leading to desirable hPSC fate patterning and functional tissue formation in 3D.
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Zhou J, Pal S, Maiti S, Davidson LA. Force production and mechanical accommodation during convergent extension. Development 2015; 142:692-701. [PMID: 25670794 PMCID: PMC4325376 DOI: 10.1242/dev.116533] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2014] [Accepted: 12/19/2014] [Indexed: 02/01/2023]
Abstract
Forces generated within the embryo during convergent extension (CE) must overcome mechanical resistance to push the head away from the rear. As mechanical resistance increases more than eightfold during CE and can vary twofold from individual to individual, we have proposed that developmental programs must include mechanical accommodation in order to maintain robust morphogenesis. To test this idea and investigate the processes that generate forces within early embryos, we developed a novel gel-based sensor to report force production as a tissue changes shape; we find that the mean stress produced by CE is 5.0±1.6 Pascal (Pa). Experiments with the gel-based force sensor resulted in three findings. (1) Force production and mechanical resistance can be coupled through myosin contractility. The coupling of these processes can be hidden unless affected tissues are challenged by physical constraints. (2) CE is mechanically adaptive; dorsal tissues can increase force production up to threefold to overcome a stiffer microenvironment. These findings demonstrate that mechanical accommodation can ensure robust morphogenetic movements against environmental and genetic variation that might otherwise perturb development and growth. (3) Force production is distributed between neural and mesodermal tissues in the dorsal isolate, and the notochord, a central structure involved in patterning vertebrate morphogenesis, is not required for force production during late gastrulation and early neurulation. Our findings suggest that genetic factors that coordinately alter force production and mechanical resistance are common during morphogenesis, and that their cryptic roles can be revealed when tissues are challenged by controlled biophysical constraints.
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Affiliation(s)
- Jian Zhou
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Siladitya Pal
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Spandan Maiti
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Lance A Davidson
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15213, USA Department of Developmental Biology, University of Pittsburgh, Pittsburgh, PA 15213, USA Department of Computational and Systems Biology, University of Pittsburgh, Pittsburgh, PA 15213, USA
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35
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Feroze R, Shawky JH, von Dassow M, Davidson LA. Mechanics of blastopore closure during amphibian gastrulation. Dev Biol 2015; 398:57-67. [PMID: 25448691 PMCID: PMC4317491 DOI: 10.1016/j.ydbio.2014.11.011] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Revised: 11/04/2014] [Accepted: 11/11/2014] [Indexed: 11/16/2022]
Abstract
Blastopore closure in the amphibian embryo involves large scale tissue reorganization driven by physical forces. These forces are tuned to generate sustained blastopore closure throughout the course of gastrulation. We describe the mechanics of blastopore closure at multiple scales and in different regions around the blastopore by characterizing large scale tissue deformations, cell level shape change and subcellular F-actin organization and by measuring tissue force production and structural stiffness of the blastopore during gastrulation. We find that the embryo generates a ramping magnitude of force until it reaches a peak force on the order of 0.5μN. During this time course, the embryo also stiffens 1.5 fold. Strain rate mapping of the dorsal, ventral and lateral epithelial cells proximal to the blastopore reveals changing patterns of strain rate throughout closure. Cells dorsal to the blastopore, which are fated to become neural plate ectoderm, are polarized and have straight boundaries. In contrast, cells lateral and ventral to the blastopore are less polarized and have tortuous cell boundaries. The F-actin network is organized differently in each region with the highest percentage of alignment occurring in the lateral region. Interestingly F-actin was consistently oriented toward the blastopore lip in dorsal and lateral cells, but oriented parallel to the lip in ventral regions. Cell shape and F-actin alignment analyses reveal different local mechanical environments in regions around the blastopore, which was reflected by the strain rate maps.
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Affiliation(s)
- Rafey Feroze
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA; School of Medicine, University of Pittsburgh Medical Center, University of Pittsburgh, Pittsburgh, PA, USA
| | - Joseph H Shawky
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA
| | - Michelangelo von Dassow
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA; Duke University Marine Lab, Beaufort, NC 28516, USA
| | - Lance A Davidson
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA; Department of Computational and Systems Biology, University of Pittsburgh, Pittsburgh, PA, USA; Department of Developmental Biology, University of Pittsburgh, Pittsburgh, PA, USA.
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36
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Jerrell RJ, Parekh A. Polyacrylamide gels for invadopodia and traction force assays on cancer cells. J Vis Exp 2015:52343. [PMID: 25590238 PMCID: PMC4354498 DOI: 10.3791/52343] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Rigid tumor tissues have been strongly implicated in regulating cancer cell migration and invasion. Invasive migration through cross-linked tissues is facilitated by actin-rich protrusions called invadopodia that proteolytically degrade the extracellular matrix (ECM). Invadopodia activity has been shown to be dependent on ECM rigidity and cancer cell contractile forces suggesting that rigidity signals can regulate these subcellular structures through actomyosin contractility. Invasive and contractile properties of cancer cells can be correlated in vitro using invadopodia and traction force assays based on polyacrylamide gels (PAAs) of different rigidities. Invasive and contractile properties of cancer cells can be correlated in vitro using invadopodia and traction force assays based on polyacrylamide gels (PAAs) of different rigidities. While some variations between the two assays exist, the protocol presented here provides a method for creating PAAs that can be used in both assays and are easily adaptable to the user's specific biological and technical needs.
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Affiliation(s)
- Rachel J Jerrell
- Department of Otolaryngology, Vanderbilt University Medical Center
| | - Aron Parekh
- Department of Otolaryngology, Vanderbilt University Medical Center;
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Gilberti RM, Knecht DA. Macrophages phagocytose nonopsonized silica particles using a unique microtubule-dependent pathway. Mol Biol Cell 2014; 26:518-29. [PMID: 25428990 PMCID: PMC4310742 DOI: 10.1091/mbc.e14-08-1301] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Cells can take up particles by both opsonized and nonopsonized pathways. Silica and latex, but not zymosan, can be taken up by the nonopsonized pathway. Uptake of silica, but not latex, is toxic to macrophages. Nonopsonized phagocytosis is characterized and found to have key differences from the complement- and antibody-opsonized pathways. Silica inhalation leads to the development of the chronic lung disease silicosis. Macrophages are killed by uptake of nonopsonized silica particles, and this is believed to play a critical role in the etiology of silicosis. However, the mechanism of nonopsonized-particle uptake is not well understood. We compared the molecular events associated with nonopsonized- and opsonized-particle phagocytosis. Both Rac and RhoA GTPases are activated upon nonopsonized-particle exposure, whereas opsonized particles activate either Rac or RhoA. All types of particles quickly generate a PI(3,4,5)P3 and F-actin response at the particle attachment site. After formation of a phagosome, the events related to endolysosome-to-phagosome fusion do not significantly differ between the pathways. Inhibitors of tyrosine kinases, actin polymerization, and the phosphatidylinositol cascade prevent opsonized- and nonopsonized-particle uptake similarly. Inhibition of silica particle uptake prevents silica-induced cell death. Microtubule depolymerization abolished uptake of complement-opsonized and nonopsonized particles but not Ab-opsonized particles. Of interest, regrowth of microtubules allowed uptake of new nonopsonized particles but not ones bound to cells in the absence of microtubules. Although complement-mediated uptake requires macrophages to be PMA-primed, untreated cells phagocytose nonopsonized silica and latex. Thus it appears that nonopsonized-particle uptake is accomplished by a pathway with unique characteristics.
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Affiliation(s)
- Renée M Gilberti
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT 06269
| | - David A Knecht
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT 06269
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Directional collective cell migration emerges as a property of cell interactions. PLoS One 2014; 9:e104969. [PMID: 25181349 PMCID: PMC4152153 DOI: 10.1371/journal.pone.0104969] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2014] [Accepted: 07/14/2014] [Indexed: 11/19/2022] Open
Abstract
Collective cell migration is a fundamental process, occurring during embryogenesis and cancer metastasis. Neural crest cells exhibit such coordinated migration, where aberrant motion can lead to fatality or dysfunction of the embryo. Migration involves at least two complementary mechanisms: contact inhibition of locomotion (a repulsive interaction corresponding to a directional change of migration upon contact with a reciprocating cell), and co-attraction (a mutual chemoattraction mechanism). Here, we develop and employ a parameterized discrete element model of neural crest cells, to investigate how these mechanisms contribute to long-range directional migration during development. Motion is characterized using a coherence parameter and the time taken to reach, collectively, a target location. The simulated cell group is shown to switch from a diffusive to a persistent state as the response-rate to co-attraction is increased. Furthermore, the model predicts that when co-attraction is inhibited, neural crest cells can migrate into restrictive regions. Indeed, inhibition of co-attraction in vivo and in vitro leads to cell invasion into restrictive areas, confirming the prediction of the model. This suggests that the interplay between the complementary mechanisms may contribute to guidance of the neural crest. We conclude that directional migration is a system property and does not require action of external chemoattractants.
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Jansen KA, Bacabac RG, Piechocka IK, Koenderink GH. Cells actively stiffen fibrin networks by generating contractile stress. Biophys J 2014; 105:2240-51. [PMID: 24268136 DOI: 10.1016/j.bpj.2013.10.008] [Citation(s) in RCA: 104] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2013] [Revised: 09/03/2013] [Accepted: 10/07/2013] [Indexed: 12/13/2022] Open
Abstract
During wound healing and angiogenesis, fibrin serves as a provisional extracellular matrix. We use a model system of fibroblasts embedded in fibrin gels to study how cell-mediated contraction may influence the macroscopic mechanical properties of their extracellular matrix during such processes. We demonstrate by macroscopic shear rheology that the cells increase the elastic modulus of the fibrin gels. Microscopy observations show that this stiffening sets in when the cells spread and apply traction forces on the fibrin fibers. We further show that the stiffening response mimics the effect of an external stress applied by mechanical shear. We propose that stiffening is a consequence of active myosin-driven cell contraction, which provokes a nonlinear elastic response of the fibrin matrix. Cell-induced stiffening is limited to a factor 3 even though fibrin gels can in principle stiffen much more before breaking. We discuss this observation in light of recent models of fibrin gel elasticity, and conclude that the fibroblasts pull out floppy modes, such as thermal bending undulations, from the fibrin network, but do not axially stretch the fibers. Our findings are relevant for understanding the role of matrix contraction by cells during wound healing and cancer development, and may provide design parameters for materials to guide morphogenesis in tissue engineering.
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Affiliation(s)
- Karin A Jansen
- Biological Soft Matter Group, FOM Institute AMOLF, Amsterdam, Netherlands
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Jerrell RJ, Parekh A. Cellular traction stresses mediate extracellular matrix degradation by invadopodia. Acta Biomater 2014; 10:1886-96. [PMID: 24412623 DOI: 10.1016/j.actbio.2013.12.058] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Revised: 11/26/2013] [Accepted: 12/30/2013] [Indexed: 12/20/2022]
Abstract
During tumorigenesis, matrix rigidity can drive oncogenic transformation via altered cellular proliferation and migration. Cells sense extracellular matrix (ECM) mechanical properties with intracellular tensile forces generated by actomyosin contractility. These contractile forces are transmitted to the matrix surface as traction stresses, which mediate mechanical interactions with the ECM. Matrix rigidity has been shown to increase proteolytic ECM degradation by cytoskeletal structures known as invadopodia that are critical for cancer progression, suggesting that cellular contractility promotes invasive behavior. However, both increases and decreases in traction stresses have been associated with metastatic behavior. Therefore, the role of cellular contractility in invasive migration leading to metastasis is unclear. To determine the relationship between cellular traction stresses and invadopodia activity, we characterized the invasive and contractile properties of an aggressive carcinoma cell line utilizing polyacrylamide gels of different rigidities. We found that ECM degradation and traction stresses were linear functions of matrix rigidity. Using calyculin A to augment myosin contractility, we also found that traction stresses were strongly predictive of ECM degradation. Overall, our data suggest that cellular force generation may play an important part in invasion and metastasis by mediating invadopodia activity in response to the mechanical properties of the tumor microenvironment.
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41
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von Dassow M, Miller CJ, Davidson LA. Biomechanics and the thermotolerance of development. PLoS One 2014; 9:e95670. [PMID: 24776615 PMCID: PMC4002435 DOI: 10.1371/journal.pone.0095670] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2013] [Accepted: 03/31/2014] [Indexed: 11/19/2022] Open
Abstract
Successful completion of development requires coordination of patterning events with morphogenetic movements. Environmental variability challenges this coordination. For example, developing organisms encounter varying environmental temperatures that can strongly influence developmental rates. We hypothesized that the mechanics of morphogenesis would have to be finely adjusted to allow for normal morphogenesis across a wide range of developmental rates. We formulated our hypothesis as a simple model incorporating time-dependent application of force to a viscoelastic tissue. This model suggested that the capacity to maintain normal morphogenesis across a range of temperatures would depend on how both tissue viscoelasticity and the forces that drive deformation vary with temperature. To test this model we investigated how the mechanical behavior of embryonic tissue (Xenopus laevis) changed with temperature; we used a combination of micropipette aspiration to measure viscoelasticity, electrically induced contractions to measure cellular force generation, and confocal microscopy to measure endogenous contractility. Contrary to expectations, the viscoelasticity of the tissues and peak contractile tension proved invariant with temperature even as rates of force generation and gastrulation movements varied three-fold. Furthermore, the relative rates of different gastrulation movements varied with temperature: the speed of blastopore closure increased more slowly with temperature than the speed of the dorsal-to-ventral progression of involution. The changes in the relative rates of different tissue movements can be explained by the viscoelastic deformation model given observed viscoelastic properties, but only if morphogenetic forces increase slowly rather than all at once.
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Affiliation(s)
- Michelangelo von Dassow
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
- Duke University Marine Laboratory, Beaufort, North Carolina, United States of America
| | - Callie Johnson Miller
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Lance A. Davidson
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
- Department of Developmental Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
- Department of Computational and Systems Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
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42
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Fischer SC, Blanchard GB, Duque J, Adams RJ, Arias AM, Guest SD, Gorfinkiel N. Contractile and mechanical properties of epithelia with perturbed actomyosin dynamics. PLoS One 2014; 9:e95695. [PMID: 24759936 PMCID: PMC3997421 DOI: 10.1371/journal.pone.0095695] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Accepted: 03/31/2014] [Indexed: 11/18/2022] Open
Abstract
Mechanics has an important role during morphogenesis, both in the generation of forces driving cell shape changes and in determining the effective material properties of cells and tissues. Drosophila dorsal closure has emerged as a reference model system for investigating the interplay between tissue mechanics and cellular activity. During dorsal closure, the amnioserosa generates one of the major forces that drive closure through the apical contraction of its constituent cells. We combined quantitation of live data, genetic and mechanical perturbation and cell biology, to investigate how mechanical properties and contraction rate emerge from cytoskeletal activity. We found that a decrease in Myosin phosphorylation induces a fluidization of amnioserosa cells which become more compliant. Conversely, an increase in Myosin phosphorylation and an increase in actin linear polymerization induce a solidification of cells. Contrary to expectation, these two perturbations have an opposite effect on the strain rate of cells during DC. While an increase in actin polymerization increases the contraction rate of amnioserosa cells, an increase in Myosin phosphorylation gives rise to cells that contract very slowly. The quantification of how the perturbation induced by laser ablation decays throughout the tissue revealed that the tissue in these two mutant backgrounds reacts very differently. We suggest that the differences in the strain rate of cells in situations where Myosin activity or actin polymerization is increased arise from changes in how the contractile forces are transmitted and coordinated across the tissue through ECadherin-mediated adhesion. Altogether, our results show that there is an optimal level of Myosin activity to generate efficient contraction and suggest that the architecture of the actin cytoskeleton and the dynamics of adhesion complexes are important parameters for the emergence of coordinated activity throughout the tissue.
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Affiliation(s)
- Sabine C. Fischer
- Buchmann Institute for Molecular Life Sciences, Department of Biological Sciences, Goethe University Frankfurt, Frankfurt am Main, Germany
| | - Guy B. Blanchard
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Julia Duque
- Centro de Biología Molecular “Severo Ochoa”, CSIC-UAM, Cantoblanco, Madrid, Spain
| | - Richard J. Adams
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Alfonso Martinez Arias
- Buchmann Institute for Molecular Life Sciences, Department of Biological Sciences, Goethe University Frankfurt, Frankfurt am Main, Germany
| | - Simon D. Guest
- Department of Engineering, University of Cambridge, Cambridge, United Kingdom
| | - Nicole Gorfinkiel
- Centro de Biología Molecular “Severo Ochoa”, CSIC-UAM, Cantoblanco, Madrid, Spain
- * E-mail:
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Itoh K, Ossipova O, Sokol SY. GEF-H1 functions in apical constriction and cell intercalations and is essential for vertebrate neural tube closure. J Cell Sci 2014; 127:2542-53. [PMID: 24681784 DOI: 10.1242/jcs.146811] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Rho family GTPases regulate many morphogenetic processes during vertebrate development including neural tube closure. Here we report a function for GEF-H1/Lfc/ArhGEF2, a RhoA-specific guanine nucleotide exchange factor that functions in neurulation in Xenopus embryos. Morpholino-mediated depletion of GEF-H1 resulted in severe neural tube defects, which were rescued by GEF-H1 RNA. Lineage tracing of GEF-H1 morphants at different developmental stages revealed abnormal cell intercalation and apical constriction, suggesting that GEF-H1 regulates these cell behaviors. Molecular marker analysis documented defects in myosin II light chain (MLC) phosphorylation, Rab11 and F-actin accumulation in GEF-H1-depleted cells. In gain-of-function studies, overexpressed GEF-H1 induced Rho-associated kinase-dependent ectopic apical constriction - marked by apical accumulation of phosphorylated MLC, γ-tubulin and F-actin in superficial ectoderm - and stimulated apical protrusive activity of deep ectoderm cells. Taken together, our observations newly identify functions of GEF-H1 in morphogenetic movements that lead to neural tube closure.
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Affiliation(s)
- Keiji Itoh
- Department of Developmental and Regenerative Biology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Olga Ossipova
- Department of Developmental and Regenerative Biology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Sergei Y Sokol
- Department of Developmental and Regenerative Biology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
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Abstract
Animal development requires a carefully orchestrated cascade of cell fate specification events and cellular movements. A surprisingly small number of choreographed cellular behaviours are used repeatedly to shape the animal body plan. Among these, cell intercalation lengthens or spreads a tissue at the expense of narrowing along an orthogonal axis. Key steps in the polarization of both mediolaterally and radially intercalating cells have now been clarified. In these different contexts, intercalation seems to require a distinct combination of mechanisms, including adhesive changes that allow cells to rearrange, cytoskeletal events through which cells exert the forces needed for cell neighbour exchange, and in some cases the regulation of these processes through planar cell polarity.
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45
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The interplay between cell signalling and mechanics in developmental processes. Nat Rev Genet 2013; 14:733-44. [PMID: 24045690 DOI: 10.1038/nrg3513] [Citation(s) in RCA: 147] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Force production and the propagation of stress and strain within embryos and organisms are crucial physical processes that direct morphogenesis. In addition, there is mounting evidence that biomechanical cues created by these processes guide cell behaviours and cell fates. In this Review we discuss key roles for biomechanics during development to directly shape tissues, to provide positional information for cell fate decisions and to enable robust programmes of development. Several recently identified molecular mechanisms suggest how cells and tissues might coordinate their responses to biomechanical cues. Finally, we outline long-term challenges in integrating biomechanics with genetic analysis of developing embryos.
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46
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The maternal-to-zygotic transition targets actin to promote robustness during morphogenesis. PLoS Genet 2013; 9:e1003901. [PMID: 24244181 PMCID: PMC3820746 DOI: 10.1371/journal.pgen.1003901] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2013] [Accepted: 09/06/2013] [Indexed: 11/26/2022] Open
Abstract
Robustness is a property built into biological systems to ensure stereotypical outcomes despite fluctuating inputs from gene dosage, biochemical noise, and the environment. During development, robustness safeguards embryos against structural and functional defects. Yet, our understanding of how robustness is achieved in embryos is limited. While much attention has been paid to the role of gene and signaling networks in promoting robust cell fate determination, little has been done to rigorously assay how mechanical processes like morphogenesis are designed to buffer against variable conditions. Here we show that the cell shape changes that drive morphogenesis can be made robust by mechanisms targeting the actin cytoskeleton. We identified two novel members of the Vinculin/α-Catenin Superfamily that work together to promote robustness during Drosophila cellularization, the dramatic tissue-building event that generates the primary epithelium of the embryo. We find that zygotically-expressed Serendipity-α (Sry-α) and maternally-loaded Spitting Image (Spt) share a redundant, actin-regulating activity during cellularization. Spt alone is sufficient for cellularization at an optimal temperature, but both Spt plus Sry-α are required at high temperature and when actin assembly is compromised by genetic perturbation. Our results offer a clear example of how the maternal and zygotic genomes interact to promote the robustness of early developmental events. Specifically, the Spt and Sry-α collaboration is informative when it comes to genes that show both a maternal and zygotic requirement during a given morphogenetic process. For the cellularization of Drosophilids, Sry-α and its expression profile may represent a genetic adaptive trait with the sole purpose of making this extreme event more reliable. Since all morphogenesis depends on cytoskeletal remodeling, both in embryos and adults, we suggest that robustness-promoting mechanisms aimed at actin could be effective at all life stages. Every embryo develops under its own unique set of circumstances, with variable inputs coming from mother, father, and the environment. To then ensure a reliable outcome, mechanisms are built into development to buffer against challenges like genetic deficiency, maternal fever, alcohol exposure, etc. This buffering, called “robustness”, can be overwhelmed, ending in miscarriage, pre-mature birth, and structural and functional birth defects. Thus, we need to understand how robustness arises in order to define an embryo's susceptibilities to genetic background and environment; and to ultimately promote healthy reproduction. In this work we provide new insight into how morphogenesis, the process of tissue building in embryos, is made more robust. First, we show that early gene expression by the embryo, or zygote, supplements the stockpile of proteins already supplied by the mother to ensure the robustness of early morphogenesis. Specifically, our data suggests that a specific gene, sry-α, and its expression by the embryo at the maternal-to-zygotic transition, is a genetic adaptation with the sole function of making the first tissue building event in the fruit fly more robust. In addition, we show that the robustness of this morphogenetic event is promoted by mechanisms regulating the actin cytoskeleton.
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Zhang H, Labouesse M. Signalling through mechanical inputs: a coordinated process. J Cell Sci 2013; 125:3039-49. [PMID: 22929901 DOI: 10.1242/jcs.093666] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
There is growing awareness that mechanical forces - in parallel to electrical or chemical inputs - have a central role in driving development and influencing the outcome of many diseases. However, we still have an incomplete understanding of how such forces function in coordination with each other and with other signalling inputs in vivo. Mechanical forces, which are generated throughout the organism, can produce signals through force-sensitive processes. Here, we first explore the mechanisms through which forces can be generated and the cellular responses to forces by discussing several examples from animal development. We then go on to examine the mechanotransduction-induced signalling processes that have been identified in vivo. Finally, we discuss what is known about the specificity of the responses to different forces, the mechanisms that might stabilize cells in response to such forces, and the crosstalk between mechanical forces and chemical signalling. Where known, we mention kinetic parameters that characterize forces and their responses. The multi-layered regulatory control of force generation, force response and force adaptation should be viewed as a well-integrated aspect in the greater biological signalling systems.
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Affiliation(s)
- Huimin Zhang
- Jiangsu Key Laboratory of Infection and Immunity, Institutes of Biology and Medical Sciences, SooChow University, SuZhou Industrial Park, SuZhou, China. [corrected]
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Wallingford JB. Planar cell polarity and the developmental control of cell behavior in vertebrate embryos. Annu Rev Cell Dev Biol 2012; 28:627-53. [PMID: 22905955 DOI: 10.1146/annurev-cellbio-092910-154208] [Citation(s) in RCA: 186] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Planar cell polarity (PCP), the orientation and alignment of cells within a sheet, is a ubiquitous cellular property that is commonly governed by the conserved set of proteins encoded by so-called PCP genes. The PCP proteins coordinate developmental signaling cues with individual cell behaviors in a wildly diverse array of tissues. Consequently, disruptions of PCP protein functions are linked to defects in axis elongation, inner ear patterning, neural tube closure, directed ciliary beating, and left/right patterning, to name only a few. This review attempts to synthesize what is known about PCP and the PCP proteins in vertebrate animals, with a particular focus on the mechanisms by which individual cells respond to PCP cues in order to execute specific cellular behaviors.
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Affiliation(s)
- John B Wallingford
- Howard Hughes Medical Institute, Section of Molecular, Cell and Developmental Biology, University of Texas, Austin, Texas 78712, USA.
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Abstract
Gastrulation is a fundamental phase of animal embryogenesis during which germ layers are specified, rearranged, and shaped into a body plan with organ rudiments. Gastrulation involves four evolutionarily conserved morphogenetic movements, each of which results in a specific morphologic transformation. During emboly, mesodermal and endodermal cells become internalized beneath the ectoderm. Epibolic movements spread and thin germ layers. Convergence movements narrow germ layers dorsoventrally, while concurrent extension movements elongate them anteroposteriorly. Each gastrulation movement can be achieved by single or multiple motile cell behaviors, including cell shape changes, directed migration, planar and radial intercalations, and cell divisions. Recent studies delineate cyclical and ratchet-like behaviors of the actomyosin cytoskeleton as a common mechanism underlying various gastrulation cell behaviors. Gastrulation movements are guided by differential cell adhesion, chemotaxis, chemokinesis, and planar polarity. Coordination of gastrulation movements with embryonic polarity involves regulation by anteroposterior and dorsoventral patterning systems of planar polarity signaling, expression of chemokines, and cell adhesion molecules.
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Affiliation(s)
- Lila Solnica-Krezel
- Department of Developmental Biology, Washington University School of Medicine in St. Louis, St. Louis, Missouri 63110, USA.
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50
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Varner VD, Taber LA. Not just inductive: a crucial mechanical role for the endoderm during heart tube assembly. Development 2012; 139:1680-90. [PMID: 22492358 DOI: 10.1242/dev.073486] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The heart is the first functioning organ to form during development. During gastrulation, the cardiac progenitors reside in the lateral plate mesoderm but maintain close contact with the underlying endoderm. In amniotes, these bilateral heart fields are initially organized as a pair of flat epithelia that move towards the embryonic midline and fuse above the anterior intestinal portal (AIP) to form the heart tube. This medial motion is typically attributed to active mesodermal migration over the underlying endoderm. In this model, the role of the endoderm is twofold: to serve as a mechanically passive substrate for the crawling mesoderm and to secrete various growth factors necessary for cardiac specification and differentiation. Here, using computational modeling and experiments on chick embryos, we present evidence supporting an active mechanical role for the endoderm during heart tube assembly. Label-tracking experiments suggest that active endodermal shortening around the AIP accounts for most of the heart field motion towards the midline. Results indicate that this shortening is driven by cytoskeletal contraction, as exposure to the myosin-II inhibitor blebbistatin arrested any shortening and also decreased both tissue stiffness (measured by microindentation) and mechanical tension (measured by cutting experiments). In addition, blebbistatin treatment often resulted in cardia bifida and abnormal foregut morphogenesis. Moreover, finite element simulations of our cutting experiments suggest that the endoderm (not the mesoderm) is the primary contractile tissue layer during this process. Taken together, these results indicate that contraction of the endoderm actively pulls the heart fields towards the embryonic midline, where they fuse to form the heart tube.
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Affiliation(s)
- Victor D Varner
- Department of Biomedical Engineering, Washington University, St Louis, MO 63130, USA
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