UMR168 – Laboratoire Physico-Chimie Curie

Publications de l’UMR 168

Année de publication : 2016

Ayako Yamada, Maéva Vignes, Cécile Bureau, Alexandre Mamane, Bastien Venzac, Stéphanie Descroix, Jean-Louis Viovy, Catherine Villard, Jean-Michel Peyrin, Laurent Malaquin (2016 May 13)

In-mold patterning and actionable axo-somatic compartmentalization for on-chip neuron culture.

Lab on a chip : 2059-68 : DOI : 10.1039/c6lc00414h En savoir plus
Résumé

Oriented neuronal networks with controlled connectivity are required for many applications ranging from studies of neurodegeneration to neuronal computation. To build such networks in vitro, an efficient, directed and long lasting guidance of axons toward their target is a pre-requisite. The best guidance achieved so far, however, relies on confining axons in enclosed microchannels, making them poorly accessible for further investigation. Here we describe a method providing accessible and highly regular arrays of axons, emanating from somas positioned in distinct compartments. This method combines the use of a novel removable partition, allowing soma positioning outside of the axon guidance patterns, and in-mold patterning (iMP), a hybrid method combining chemical and mechanical cell positioning clues applied here for the first time to neurons. The axon guidance efficiency of iMP is compared to that of conventional patterning methods, e.g. micro-contact printing (chemical constraints by a poly-l-lysine motif) and micro-grooves (physical constraints by homogeneously coated microstructures), using guiding tracks of different widths and spacing. We show that iMP provides a gain of 10 to 100 in axon confinement efficiency on the tracks, yielding mm-long, highly regular, and fully accessible on-chip axon arrays. iMP also allows well-defined axon guidance from small populations of several neurons confined at predefined positions in μm-sized wells. iMP will thus open new routes for the construction of complex and accurately controlled neuronal networks.

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Davide Ferraro, Jérôme Champ, Bruno Teste, Marco Serra, Laurent Malaquin, Jean-Louis Viovy, Patricia de Cremoux, Stephanie Descroix (2016 May 10)

Microfluidic platform combining droplets and magnetic tweezers: application to HER2 expression in cancer diagnosis.

Scientific reports : 25540 : DOI : 10.1038/srep25540 En savoir plus
Résumé

The development of precision medicine, together with the multiplication of targeted therapies and associated molecular biomarkers, call for major progress in genetic analysis methods, allowing increased multiplexing and the implementation of more complex decision trees, without cost increase or loss of robustness. We present a platform combining droplet microfluidics and magnetic tweezers, performing RNA purification, reverse transcription and amplification in a fully automated and programmable way, in droplets of 250nL directly sampled from a microtiter-plate. This platform decreases sample consumption about 100 fold as compared to current robotized platforms and it reduces human manipulations and contamination risk. The platform’s performance was first evaluated on cell lines, showing robust operation on RNA quantities corresponding to less than one cell, and then clinically validated with a cohort of 21 breast cancer samples, for the determination of their HER2 expression status, in a blind comparison with an established routine clinical analysis.

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Jean-Francois Rupprecht, Jacques Prost (2016 Apr 30)

PHYSICAL BIOLOGY. A fresh eye on nonequilibrium systems.

Science (New York, N.Y.) : 514-5 : DOI : 10.1126/science.aaf4611 En savoir plus
Résumé

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Alexander Y Grosberg, Jean-François Joanny, Watee Srinin, Yitzhak Rabin (2016 Apr 28)

Scale-Dependent Viscosity in Polymer Fluids.

The journal of physical chemistry. B En savoir plus
Résumé

In this communication, we use simple physical arguments to construct a « phase diagram » of various frequency and wave vector-dependent regimes of effective viscosity for polymer fluids, including nonentangled and entangled melts, semidilute solutions without and with hydrodynamic interactions, as well as the more exotic case of a melt of unconcatenated ring polymers.

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Laura Wagstaff, Maja Goschorska, Kasia Kozyrska, Guillaume Duclos, Iwo Kucinski, Anatole Chessel, Lea Hampton-O'Neil, Charles R Bradshaw, George E Allen, Emma L Rawlins, Pascal Silberzan, Rafael E Carazo Salas, Eugenia Piddini (2016 Apr 26)

Mechanical cell competition kills cells via induction of lethal p53 levels.

Nature communications : 11373 : DOI : 10.1038/ncomms11373 En savoir plus
Résumé

Cell competition is a quality control mechanism that eliminates unfit cells. How cells compete is poorly understood, but it is generally accepted that molecular exchange between cells signals elimination of unfit cells. Here we report an orthogonal mechanism of cell competition, whereby cells compete through mechanical insults. We show that MDCK cells silenced for the polarity gene scribble (scrib(KD)) are hypersensitive to compaction, that interaction with wild-type cells causes their compaction and that crowding is sufficient for scrib(KD) cell elimination. Importantly, we show that elevation of the tumour suppressor p53 is necessary and sufficient for crowding hypersensitivity. Compaction, via activation of Rho-associated kinase (ROCK) and the stress kinase p38, leads to further p53 elevation, causing cell death. Thus, in addition to molecules, cells use mechanical means to compete. Given the involvement of p53, compaction hypersensitivity may be widespread among damaged cells and offers an additional route to eliminate unfit cells.

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Vincent Nier, Shreyansh Jain, Chwee Teck Lim, Shuji Ishihara, Benoit Ladoux, Philippe Marcq (2016 Apr 14)

Inference of Internal Stress in a Cell Monolayer.

Biophysical journal : 1625-35 : DOI : 10.1016/j.bpj.2016.03.002 En savoir plus
Résumé

We combine traction force data with Bayesian inversion to obtain an absolute estimate of the internal stress field of a cell monolayer. The method, Bayesian inversion stress microscopy, is validated using numerical simulations performed in a wide range of conditions. It is robust to changes in each ingredient of the underlying statistical model. Importantly, its accuracy does not depend on the rheology of the tissue. We apply Bayesian inversion stress microscopy to experimental traction force data measured in a narrow ring of cohesive epithelial cells, and check that the inferred stress field coincides with that obtained by direct spatial integration of the traction force data in this quasi one-dimensional geometry.

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Casimir Emako, Charlène Gayrard, Axel Buguin, Luís Neves de Almeida, Nicolas Vauchelet (2016 Apr 13)

Traveling Pulses for a Two-Species Chemotaxis Model.

PLoS computational biology : e1004843 : DOI : 10.1371/journal.pcbi.1004843 En savoir plus
Résumé

Mathematical models have been widely used to describe the collective movement of bacteria by chemotaxis. In particular, bacterial concentration waves traveling in a narrow channel have been experimentally observed and can be precisely described thanks to a mathematical model at the macroscopic scale. Such model was derived in [1] using a kinetic model based on an accurate description of the mesoscopic run-and-tumble process. We extend this approach to study the behavior of the interaction between two populations of E. Coli. Separately, each population travels with its own speed in the channel. When put together, a synchronization of the speed of the traveling pulses can be observed. We show that this synchronization depends on the fraction of the fast population. Our approach is based on mathematical analysis of a macroscopic model of partial differential equations. Numerical simulations in comparison with experimental observations show qualitative agreement.

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Ken Sekimoto, Jacques Prost (2016 Mar 31)

Elastic Anisotropy Scenario for Cooperative Binding of Kinesin-Coated Beads on Microtubules.

The journal of physical chemistry. B En savoir plus
Résumé

Muto et al. reported in 2005 an observation called cooperative binding, according to which the initial binding of a bead covered with active kinesins on a microtubule filament was capable of favoring the subsequent binding of similar beads on the same filament up to distances of the order of a few microns. This positive bias is stronger ahead of the initially bound bead than behind. We explain this effect by combining the recently proposed notion of shear screening length with the notion of localized tubulin conformational transition induced by motor binding. Elastic terms linked to the polarity of protofilaments, up to now ignored, provide adequate description to the long-range elastic shear generated by motor binding. The subsequent binding is favored when and where the shear displacement of protofilaments meets the requirement for specific strong binding. We propose experimental tests of our model, which open the way to a new type of spectroscopy for biomolecular processes.

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Konstantinos D Kokkaliaris, Daniel Lucas, Isabel Beerman, David G Kent, Leïla Perié (2016 Mar 22)

Understanding hematopoiesis from a single-cell standpoint.

Experimental hematology : 447-50 : DOI : 10.1016/j.exphem.2016.03.003 En savoir plus
Résumé

The cellular diversity of the hematopoietic system has been extensively studied, and a plethora of cell surface markers have been used to discriminate and prospectively purify different blood cell types. However, even within phenotypically identical fractions of hematopoietic stem and progenitor cells or lineage-restricted progenitors, significant functional heterogeneity is observed when single cells are analyzed. To address these challenges, researchers are now using techniques to follow single cells and their progeny to improve our understanding of the underlying functional heterogeneity. On November 19, 2015, Dr. David Kent and Dr. Leïla Perié, two emerging young group leaders, presented their recent efforts to dissect the functional properties of individual cells with a webinar series organized by the International Society for Experimental Hematology. Here, we provide a summary of the presented methods for cell labeling and clonal tracking and discuss how these different techniques have been employed to study hematopoiesis.

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Edouard Hannezo, Alice Coucke, Jean-François Joanny (2016 Mar 18)

Interplay of migratory and division forces as a generic mechanism for stem cell patterns.

Physical review. E : 022405 En savoir plus
Résumé

In many adult tissues, stem cells and differentiated cells are not homogeneously distributed: stem cells are arranged in periodic « niches, » and differentiated cells are constantly produced and migrate out of these niches. In this article, we provide a general theoretical framework to study mixtures of dividing and actively migrating particles, which we apply to biological tissues. We show in particular that the interplay between the stresses arising from active cell migration and stem cell division give rise to robust stem cell patterns. The instability of the tissue leads to spatial patterns which are either steady or oscillating in time. The wavelength of the instability has an order of magnitude consistent with the biological observations. We also discuss the implications of these results for future in vitro and in vivo experiments.

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Nicolas Borghi, Emmanuel Farge, Christophe Lavelle (2016 Feb 21)

Experimental approaches in mechanotransduction: From molecules to pathology.

Methods (San Diego, Calif.) : 1-3 : DOI : 10.1016/j.ymeth.2016.01.007 En savoir plus
Résumé

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Pierre Recho, Jonas Ranft, Philippe Marcq (2016 Jan 23)

One-dimensional collective migration of a proliferating cell monolayer.

Soft matter : 2381-91 : DOI : 10.1039/c5sm02857d En savoir plus
Résumé

The importance of collective cellular migration during embryogenesis and tissue repair asks for a sound understanding of underlying principles and mechanisms. Here, we address recent in vitro experiments on cell monolayers, which show that the advancement of the leading edge relies on cell proliferation and protrusive activity at the tissue margin. Within a simple viscoelastic mechanical model amenable to detailed analysis, we identify a key parameter responsible for tissue expansion, and we determine the dependence of the monolayer velocity as a function of measurable rheological parameters. Our results allow us to discuss the effects of pharmacological perturbations on the observed tissue dynamics.

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Aurélie Bertin, Eva Nogales (2016 Jan 15)

Characterization of Septin Ultrastructure in Budding Yeast Using Electron Tomography.

Methods in molecular biology (Clifton, N.J.) : 113-23 : DOI : 10.1007/978-1-4939-3145-3_9 En savoir plus
Résumé

Septins are essential for the completion of cytokinesis. In budding yeast, Saccharomyces cerevisiae, septins are located at the bud neck during mitosis and are closely connected to the inner plasma membrane. In vitro, yeast septins have been shown to self-assemble into a variety of filamentous structures, including rods, paired filaments, bundles, and rings (Bertin et al. Proc Natl Acad Sci U S A, 105(24):8274-8279, 2008; Garcia et al. J Cell Biol, 195(6):993-1004, 2011; Bertin et al. J Mol Biol, 404(4):711-731, 2010). Using electron tomography of freeze-substituted sections and cryo-electron tomography of frozen sections, we determined the three-dimensional organization of the septin cytoskeleton in dividing budding yeast with molecular resolution (Bertin et al. Mol Biol Cell, 23(3):423-432, 2012; Bertin and Nogales. Commun Integr Biol 5(5):503-505, 2012). Here, we describe the detailed procedures used for our characterization of the septin cellular ultrastructure.

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Tom S Weber, Leïla Perié, Ken R Duffy (2016 Jan 7)

Inferring average generation via division-linked labeling.

Journal of mathematical biology En savoir plus
Résumé

For proliferating cells subject to both division and death, how can one estimate the average generation number of the living population without continuous observation or a division-diluting dye? In this paper we provide a method for cell systems such that at each division there is an unlikely, heritable one-way label change that has no impact other than to serve as a distinguishing marker. If the probability of label change per cell generation can be determined and the proportion of labeled cells at a given time point can be measured, we establish that the average generation number of living cells can be estimated. Crucially, the estimator does not depend on knowledge of the statistics of cell cycle, death rates or total cell numbers. We explore the estimator’s features through comparison with physiologically parameterized stochastic simulations and extrapolations from published data, using it to suggest new experimental designs.

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Chaigne A, Campillo C, Voituriez R, Gov NS, Sykes C, Verlhac MH, Terret ME (2016 Jan 4)

F-actin mechanics control spindle centring in the mouse zygote

Nature Communications : 7 : 10253 : DOI : 10.1038/ncomms10253 En savoir plus
Résumé

Mitotic spindle position relies on interactions between astral microtubules nucleated by centrosomes and a rigid cortex. Some cells, such as mouse oocytes, do not possess centrosomes and astral microtubules. These cells rely only on actin and on a soft cortex to position their spindle off-centre and undergo asymmetric divisions. While the first mouse embryonic division also occurs in the absence of centrosomes, it is symmetric and not much is known on how the spindle is positioned at the exact cell centre. Using interdisciplinary approaches, we demonstrate that zygotic spindle positioning follows a three-step process: (1) coarse centring of pronuclei relying on the dynamics of an F-actin/Myosin-Vb meshwork; (2) fine centring of the metaphase plate depending on a high cortical tension; (3) passive maintenance at the cell centre. Altogether, we show that F-actin-dependent mechanics operate the switch between asymmetric to symmetric division required at the oocyte to embryo transition.

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