UMR168 – Laboratoire Physico-Chimie Curie

Publications de l’UMR 168

Année de publication : 2015

D Ferraro, Y Lin, B Teste, D Talbot, L Malaquin, S Descroix, A Abou-Hassan (2015 Oct 6)

Continuous chemical operations and modifications on magnetic γ-Fe2O3 nanoparticles confined in nanoliter droplets for the assembly of fluorescent and magnetic SiO2@γ-Fe2O3.

Chemical communications (Cambridge, England) : 16904-7 : DOI : 10.1039/c5cc07044a En savoir plus
Résumé

We present a microfluidic platform that allows undergoing different chemical operations in a nanoliter droplet starting from the colloidal suspension of magnetic iron oxide (γ-Fe2O3) nanoparticles « NPs » (ferrofluid). These operations include: mixing, flocculation, magnetic decantation, colloidal redispersion, washing, surface functionalization, heating and colloidal assembly. To prove the platform capabilities, we produced fluorescent and magnetic nanoassemblies composed of fluorescent silica and magnetic NPs.

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Monica Rolando, Caroline Stefani, Anne Doye, Maria I Acosta, Orane Visvikis, Hannah G Yevick, Carmen Buchrieser, Amel Mettouchi, Patricia Bassereau, Emmanuel Lemichez (2015 Sep 26)

Contractile actin cables induced by Bacillus anthracis lethal toxin depend on the histone acetylation machinery.

Cytoskeleton (Hoboken, N.J.) : 542-56 : DOI : 10.1002/cm.21256 En savoir plus
Résumé

It remains a challenge to decode the molecular basis of the long-term actin cytoskeleton rearrangements That are-governed by the reprogramming of gene expression. Bacillus anthracis lethal toxin (LT) Inhibits mitogen-activated protein kinase (MAPK) signaling, thereby modulating gene expression, with major consequences for actin cytoskeleton organization and the loss of endothelial barrier function. Using a laser ablation approach, we caractérisé the contractile and tensile mechanical properties of LT-induced stress fibers. These actin cables resist pulling force That Transmitted are at cell-matrix interfaces and at cell-cell adherens junctions discontinuous. We carry That Treating the cells with trichostatin A (TSA), a broad inhibitor of histone deacetylases Range (HDACs), or with MS-275, qui targets HDAC1, 2 and 3, induces stress fibers. LT Decreased the cellular levels of HDAC1, 2 and 3 and the Reduced total HDAC activity in the nucleus. Both the LT and TSA treatments Rnd3 induced expression, qui est required for the LT-mediated induction of actin stress fibers. Furthermore, we reveal That Treating the cells intoxicated with LT-garcinol, an inhibitor of histone acetyl transferases (HATs) disrupts the stress fibers and limits the monolayer barrier dysfunctions. These data Demonstrate the importance of modulating the flow of protein acetylation in order to control actin cytoskeleton organization and the endothelial cell monolayer barrier.

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Maria-Elena Fernandez-Sanchez, Thibaut Brunet, Jens-Christian Röper, Emmanuel Farge (2015 Sep 24)

Mechanotransduction’s impact on animal development, evolution, and tumorigenesis.

Annual review of cell and developmental biology : 373-97 : DOI : 10.1146/annurev-cellbio-102314-112441 En savoir plus
Résumé

Mechanotransduction translates mechanical signals into biochemical signals. It is based on the soft-matter properties of biomolecules or membranes that deform in response to mechanical loads to trigger activation of biochemical reactions. The study of mechanotransductive processes in cell-structure organization has been initiated in vitro in many biological contexts, such as examining cells’ response to substrate rigidity increases associated with tumor fibrosis and to blood flow pressure. In vivo, the study of mechanotransduction in regulating physiological processes has focused primarily on the context of embryogenesis, with an increasing number of examples demonstrating its importance for both differentiation and morphogenesis. The conservation across species of mechanical induction in early embryonic patterning now suggests that major animal transitions, such as mesoderm emergence, may have been based on mechanotransduction pathways. In adult animal tissues, permanent stiffness and tissue growth pressure contribute to tumorigenesis and appear to reactivate such conserved embryonic mechanosensitive pathways.

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Delabre U, Feld K, Crespo E, Whyte G, Sykes C, Seifert U, Guck J (2015 Aug 14)

Deformation of phospholipid vesicles in an optical stretcher

Soft Matter : 11 : 6075-88 : DOI : 10.1039/c5sm00562k En savoir plus
Résumé

Phospholipid vesicles are common model systems for cell membranes. Important aspects of the membrane function relate to its mechanical properties. Here we have investigated the deformation behaviour of phospholipid vesicles in a dual-beam laser trap, also called an optical stretcher. This study explicitly makes use of the inherent heating present in such traps to investigate the dependence of vesicle deformation on temperature. By using lasers with different wavelengths, optically induced mechanical stresses and temperature increase can be tuned fairly independently with a single setup. The phase transition temperature of vesicles can be clearly identified by an increase in deformation. In the case of no heating effects, a minimal model for drop deformation in an optical stretcher and a more specific model for vesicle deformation that takes explicitly into account the angular dependence of the optical stress are presented to account for the experimental results. Elastic constants are extracted from the fitting procedures, which agree with literature data. This study demonstrates the utility of optical stretching, which is easily combined with microfluidic delivery, for the future serial, high-throughput study of the mechanical and thermodynamic properties of phospholipid vesicles.

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Byung-Kuk Yoo, Axel Buguin, Zoher Gueroui (2015 Jul 30)

Biochemical perturbations of the mitotic spindle in Xenopus extracts using a diffusion-based microfluidic assay.

Biomicrofluidics : 044101 : DOI : 10.1063/1.4926324 En savoir plus
Résumé

A microfluidic device is a powerful tool to manipulate in a controlled manner at spatiotemporal scales for biological systems. Here, we describe a simple diffusion-based assay to generate and measure the effect of biochemical perturbations within the cytoplasm of cell-free extracts from Xenopus eggs. Our approach comprises a microliter reservoir and a model cytoplasm that are separated by a synthetic membrane containing sub-micrometric pores through which small molecules and recombinant proteins can diffuse. We have used this system to examine the perturbation of elements of the mitotic spindle, which is a microtubule-based bipolar structure involved in the segregation of the replicated genome to daughter cells during cell division. First, we used the small molecule inhibitor monastrol to target kinesin-5, a molecular motor that maintains the microtubule spindle bipolarity. Next, we explored the dynamics of the mitotic spindle by monitoring the exchange between unpolymerized and polymerized tubulin within microtubule fibers. These results show that a simple diffusion-based system can generate biochemical perturbations directly within a cell-free cytoplasm based on Xenopus egg extracts at the time scale of minutes. Our assay is therefore suitable for monitoring the dynamics of supramolecular assemblies within cell-free extracts in response to perturbations. This strategy opens up broad perspectives including phenotype screening or mechanistic studies of biological assembly processes and could be applied to other cell-free extracts such as those derived from mammalian or bacterial cells.

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Thanh Duc Mai, Iago Pereiro, Mohamed Hiraoui, Jean-Louis Viovy, Stéphanie Descroix, Myriam Taverna, Claire Smadja (2015 Jul 25)

Magneto-immunocapture with on-bead fluorescent labeling of amyloid-β peptides: towards a microfluidized-bed-based operation.

The Analyst : 5891-900 : DOI : 10.1039/c5an01179e En savoir plus
Résumé

A new sample treatment approach for sensitive determination of three amyloid-β peptides (Aβ 1-42, Aβ 1-40 and Aβ 1-38) with capillary electrophoresis coupled with laser induced fluorescent detection is reported herein. These Aβ peptides are considered an important family of biomarkers in the cerebrospinal fluid (CSF) for early diagnosis of Alzheimer’s disease (AD). Due to their extremely low abundance in CSF (down to sub nM ranges), batch-wise preconcentration via magneto-immunocapture with enrichment factors up to 100 was implemented. The Aβ peptides were first captured onto magnetic micro-beads. Then, on-beads fluorescent labeling of the captured Aβ peptides were carried out to avoid the unwanted presence of extra fluorescent dye in the eluent as in the case of in-solution labeling. Finally thermal elution was performed and eluted labeled peptides were analyzed off line with CE-LIF. The Aβ-capturing efficiencies of different commercially available antibodies grafted onto magnetic beads were tested. Aβ peptides in CSF samples collected from AD’s patients and healthy persons (used as controls) were measured and evaluated. As a proof of concept, the developed strategy was adapted into a miniaturized fluidized bed configuration that has the potential for coupling with a microchip separation system.

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Vincent Nier, Maxime Deforet, Guillaume Duclos, Hannah G Yevick, Olivier Cochet-Escartin, Philippe Marcq, Pascal Silberzan (2015 Jul 21)

Tissue fusion over nonadhering surfaces.

Proceedings of the National Academy of Sciences of the United States of America : 9546-51 : DOI : 10.1073/pnas.1501278112 En savoir plus
Résumé

Tissue fusion eliminates physical voids in a tissue to form a continuous structure and is central to many processes in development and repair. Fusion events in vivo, particularly in embryonic development, often involve the purse-string contraction of a pluricellular actomyosin cable at the free edge. However, in vitro, adhesion of the cells to their substrate favors a closure mechanism mediated by lamellipodial protrusions, which has prevented a systematic study of the purse-string mechanism. Here, we show that monolayers can cover well-controlled mesoscopic nonadherent areas much larger than a cell size by purse-string closure and that active epithelial fluctuations are required for this process. We have formulated a simple stochastic model that includes purse-string contractility, tissue fluctuations, and effective friction to qualitatively and quantitatively account for the dynamics of closure. Our data suggest that, in vivo, tissue fusion adapts to the local environment by coordinating lamellipodial protrusions and purse-string contractions.

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Leïla Perié, Ken R Duffy, Lianne Kok, Rob J de Boer, Ton N Schumacher (2015 Jul 20)

The Branching Point in Erythro-Myeloid Differentiation.

Cell : 1655-62 : DOI : 10.1016/j.cell.2015.11.059 En savoir plus
Résumé

Development of mature blood cell progenies from hematopoietic stem cells involves the transition through lineage-restricted progenitors. The first branching point along this developmental process is thought to separate the erythro-myeloid and lymphoid lineage fate by yielding two intermediate progenitors, the common myeloid and the common lymphoid progenitors (CMPs and CLPs). Here, we use single-cell lineage tracing to demonstrate that so-called CMPs are highly heterogeneous with respect to cellular output, with most individual CMPs yielding either only erythrocytes or only myeloid cells after transplantation. Furthermore, based on the labeling of earlier progenitors, we show that the divergence between the myeloid and erythroid lineage develops within multipotent progenitors (MPP). These data provide evidence for a model of hematopoietic branching in which multiple distinct lineage commitments occur in parallel within the MPP pool.

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Sens P, Plastino J (2015 Jul 15)

Membrane tension and cytoskeleton organization in cell motility

Journal of Physics: Condensed Matter : 27 : 273103 : DOI : 10.1088/0953-8984/27/27/273103 En savoir plus
Résumé

Cell membrane shape changes are important for many aspects of normal biological function, such as tissue development, wound healing and cell division and motility. Various disease states are associated with deregulation of how cells move and change shape, including notably tumor initiation and cancer cell metastasis. Cell motility is powered, in large part, by the controlled assembly and disassembly of the actin cytoskeleton. Much of this dynamic happens in close proximity to the plasma membrane due to the fact that actin assembly factors are membrane-bound, and thus actin filaments are generally oriented such that their growth occurs against or near the membrane. For a long time, the membrane was viewed as a relatively passive scaffold for signaling. However, results from the last five years show that this is not the whole picture, and that the dynamics of the actin cytoskeleton are intimately linked to the mechanics of the cell membrane. In this review, we summarize recent findings concerning the role of plasma membrane mechanics in cell cytoskeleton dynamics and architecture, showing that the cell membrane is not just an envelope or a barrier for actin assembly, but is a master regulator controlling cytoskeleton dynamics and cell polarity.

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María Elena Fernández-Sánchez, Sandrine Barbier, Joanne Whitehead, Gaëlle Béalle, Aude Michel, Heldmuth Latorre-Ossa, Colette Rey, Laura Fouassier, Audrey Claperon, Laura Brullé, Elodie Girard, Nicolas Servant, Thomas Rio-Frio, Hélène Marie, Sylviane Lesieur, Chantal Housset, Jean-Luc Gennisson, Mickaël Tanter, Christine Ménager, Silvia Fre, Sylvie Robine, Emmanuel Farge (2015 Jul 2)

Mechanical induction of the tumorigenic β-catenin pathway by tumour growth pressure.

Nature : 92-5 : DOI : 10.1038/nature14329 En savoir plus
Résumé

The tumour microenvironment may contribute to tumorigenesis owing to mechanical forces such as fibrotic stiffness or mechanical pressure caused by the expansion of hyper-proliferative cells. Here we explore the contribution of the mechanical pressure exerted by tumour growth onto non-tumorous adjacent epithelium. In the early stage of mouse colon tumour development in the Notch(+)Apc(+/1638N) mouse model, we observed mechanistic pressure stress in the non-tumorous epithelial cells caused by hyper-proliferative adjacent crypts overexpressing active Notch, which is associated with increased Ret and β-catenin signalling. We thus developed a method that allows the delivery of a defined mechanical pressure in vivo, by subcutaneously inserting a magnet close to the mouse colon. The implanted magnet generated a magnetic force on ultra-magnetic liposomes, stabilized in the mesenchymal cells of the connective tissue surrounding colonic crypts after intravenous injection. The magnetically induced pressure quantitatively mimicked the endogenous early tumour growth stress in the order of 1,200 Pa, without affecting tissue stiffness, as monitored by ultrasound strain imaging and shear wave elastography. The exertion of pressure mimicking that of tumour growth led to rapid Ret activation and downstream phosphorylation of β-catenin on Tyr654, imparing its interaction with the E-cadherin in adherens junctions, and which was followed by β-catenin nuclear translocation after 15 days. As a consequence, increased expression of β-catenin-target genes was observed at 1 month, together with crypt enlargement accompanying the formation of early tumorous aberrant crypt foci. Mechanical activation of the tumorigenic β-catenin pathway suggests unexplored modes of tumour propagation based on mechanical signalling pathways in healthy epithelial cells surrounding the tumour, which may contribute to tumour heterogeneity.

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Edouard Hannezo, Bo Dong, Pierre Recho, Jean-François Joanny, Shigeo Hayashi (2015 Jun 17)

Cortical instability drives periodic supracellular actin pattern formation in epithelial tubes.

Proceedings of the National Academy of Sciences of the United States of America : 8620-5 : DOI : 10.1073/pnas.1504762112 En savoir plus
Résumé

An essential question of morphogenesis is how patterns arise without preexisting positional information, as inspired by Turing. In the past few years, cytoskeletal flows in the cell cortex have been identified as a key mechanism of molecular patterning at the subcellular level. Theoretical and in vitro studies have suggested that biological polymers such as actomyosin gels have the property to self-organize, but the applicability of this concept in an in vivo setting remains unclear. Here, we report that the regular spacing pattern of supracellular actin rings in the Drosophila tracheal tubule is governed by a self-organizing principle. We propose a simple biophysical model where pattern formation arises from the interplay of myosin contractility and actin turnover. We validate the hypotheses of the model using photobleaching experiments and report that the formation of actin rings is contractility dependent. Moreover, genetic and pharmacological perturbations of the physical properties of the actomyosin gel modify the spacing of the pattern, as the model predicted. In addition, our model posited a role of cortical friction in stabilizing the spacing pattern of actin rings. Consistently, genetic depletion of apical extracellular matrix caused strikingly dynamic movements of actin rings, mirroring our model prediction of a transition from steady to chaotic actin patterns at low cortical friction. Our results therefore demonstrate quantitatively that a hydrodynamical instability of the actin cortex can trigger regular pattern formation and drive morphogenesis in an in vivo setting.

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Pierre Sens, Julie Plastino (2015 Jun 11)

Membrane tension and cytoskeleton organization in cell motility.

Journal of physics. Condensed matter : an Institute of Physics journal : 273103 : DOI : 10.1088/0953-8984/27/27/273103 En savoir plus
Résumé

Cell membrane shape changes are important for many aspects of normal biological function, such as tissue development, wound healing and cell division and motility. Various disease states are associated with deregulation of how cells move and change shape, including notably tumor initiation and cancer cell metastasis. Cell motility is powered, in large part, by the controlled assembly and disassembly of the actin cytoskeleton. Much of this dynamic happens in close proximity to the plasma membrane due to the fact that actin assembly factors are membrane-bound, and thus actin filaments are generally oriented such that their growth occurs against or near the membrane. For a long time, the membrane was viewed as a relatively passive scaffold for signaling. However, results from the last five years show that this is not the whole picture, and that the dynamics of the actin cytoskeleton are intimately linked to the mechanics of the cell membrane. In this review, we summarize recent findings concerning the role of plasma membrane mechanics in cell cytoskeleton dynamics and architecture, showing that the cell membrane is not just an envelope or a barrier for actin assembly, but is a master regulator controlling cytoskeleton dynamics and cell polarity.

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Mijo Simunovic, Ka Yee C Lee, Patricia Bassereau (2015 May 29)

Celebrating Soft Matter’s 10th anniversary: screening of the calcium-induced spontaneous curvature of lipid membranes.

Soft matter : 5030-6 : DOI : 10.1039/c5sm00104h En savoir plus
Résumé

Lipid membranes are key regulators of cellular function. An significant step in membrane-related phenomena is the reshaping of the lipid bilayer, Often induced by binding of macromolecules. Numerous experimental and simulation efforts-have Revealed That calcium, a ubiquitous cellular messenger: has a strong impact on the behavior stage, structural properties, and the stability of membranes. Yet, it is still unknown the way calcium and lipid interactions affect Their macroscopic mechanical properties. In this work, we Studied the interaction of calcium ions with membrane tethers pulled from giant unilamellar vesicles, QUANTIFY to the mechanical effect on the membrane. We found calcium That imposed a positive spontaneous curvature is Negatively charged membranes Contrary to predictions we made based on the Proposed atomic structure. Surprisingly, this effect vanishes in the presence of physiologically relevant concentrations of sodium chloride. Our work Implies That calcium May be a trigger for reshaping membrane only at high concentrations, in a process robustly That is screened by sodium ions.

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Yevick HG, Duclos G, Bonnet I, Silberzan P. (2015 May 12)

Architecture and migration of an epithelium on a cylindrical wire

Proc Natl Acad Sci USA112(19):5944-9 : DOI : 10.1073/pnas.1418857112 En savoir plus
Résumé

In a wide range of epithelial tissues such as kidney tubules or breast acini, cells organize into bidimensional monolayers experiencing an out-of-plane curvature. Cancer cells can also migrate collectively from epithelial tumors by wrapping around vessels or muscle fibers. However, in vitro experiments dealing with epithelia are mostly performed on flat substrates, neglecting this out-of-plane component. In this paper, we study the development and migration of epithelial tissues on glass wires of well-defined radii varying from less than 1 µm up to 85 µm. To uncouple the effect of out-of-plane curvature from the lateral confinement experienced by the cells in these geometries, we compare our results to experiments performed on narrow adhesive tracks. Because of lateral confinement, the velocity of collective migration increases for radii smaller than typically 20 µm. The monolayer dynamics is then controlled by front-edge protrusions. Conversely, high curvature is identified as the inducer of frequent cell detachments at the front edge, a phenotype reminiscent of the Epithelial-Mesenchymal Transition. High curvature also induces a circumferential alignment of the actin cytoskeleton, stabilized by multiple focal adhesions. This organization of the cytoskeleton is reminiscent of in vivo situations such as the development of the trachea of the Drosophila embryo. Finally, submicron radii halt the monolayer, which then reconfigures into hollow cysts.

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Sham Tlili, Cyprien Gay, François Graner, Philippe Marcq, François Molino, Pierre Saramito (2015 May 10)

Colloquium: Mechanical formalisms for tissue dynamics.

The European physical journal. E, Soft matter : 121 : DOI : 10.1140/epje/i2015-15033-4 En savoir plus
Résumé

The understanding of morphogenesis in living organisms has been renewed by tremendous progress in experimental techniques that provide access to cell scale, quantitative information both on the shapes of cells within tissues and on the genes being expressed. This information suggests that our understanding of the respective contributions of gene expression and mechanics, and of their crucial entanglement, will soon leap forward. Biomechanics increasingly benefits from models, which assist the design and interpretation of experiments, point out the main ingredients and assumptions, and ultimately lead to predictions. The newly accessible local information thus calls for a reflection on how to select suitable classes of mechanical models. We review both mechanical ingredients suggested by the current knowledge of tissue behaviour, and modelling methods that can help generate a rheological diagram or a constitutive equation. We distinguish cell scale (« intra-cell ») and tissue scale (« inter-cell ») contributions. We recall the mathematical framework developed for continuum materials and explain how to transform a constitutive equation into a set of partial differential equations amenable to numerical resolution. We show that when plastic behaviour is relevant, the dissipation function formalism appears appropriate to generate constitutive equations; its variational nature facilitates numerical implementation, and we discuss adaptations needed in the case of large deformations. The present article gathers theoretical methods that can readily enhance the significance of the data to be extracted from recent or future high throughput biomechanical experiments.

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