BIORXIV, 2019

Different integrins mediate haptotaxis of T lymphocytes towards either lower or higher adhesion zones

Xuan Luo, Laurene Aoun, Martine Biarnes-Pelicot, Pierre-Olivier Strale, Vincent Studer, Marie-Pierre Valignat, Olivier Theodoly
Guidance of cells by molecules anchored on a substrate, known as haptotaxis, is arguably crucial in development, immunology and cancer, however the exact cues and mechanisms driving cell orientation in vivo are hardly identified. Adhesive haptotaxis has been described in the case of mesenchymatous cells that develop strong pulling forces with their substrates and orient via a tug of war mechanism, a competition between cells pulling edges. In the case of amoeboid cells that migrate with minimal interaction with their substrate, existence of adhesive haptotaxis remains unclear. …
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BIORXIV, 2018

Forces and constraints controlling podosome assembly and disassembly

Nisha Mohd Rafiq, Gianluca Grenci, Michael M Kozlov, Gareth E Jones, Virgile Viasnoff, Alexander D Bershadsky
Podosomes are a singular category of integrin-mediated adhesions important in the processes of cell migration, matrix degradation, and cancer cell invasion. Despite a wealth of biochemical studies, the effects of mechanical forces on podosome integrity and dynamics are poorly understood. Here, we show that podosomes are highly sensitive to two groups of physical factors. First, we describe the process of podosome disassembly induced by activation of myosin- IIA filament assembly. …
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PLOS One, 2018

Live nanoscopic to mesoscopic topography reconstruction with an optical microscope for chemical and biological samples

Olivier Theodoly, Nicolas Garcia-Seyda, Fréderic Bedu, Xuan Luo, Sylvain Gabriele, Tâm Mignot, Joanna Giermanska, Jean-Paul Chapel, Mélinda Métivier, Marie-Pierre Valignat
Macroscopic properties of physical and biological processes like friction, wetting, and adhesion or cell migration are controlled by interfacial properties at the nanoscopic scale. In an attempt to bridge simultaneously investigations at different scales, we demonstrate here how optical microscopy in Wet-Surface Ellipsometric Enhanced Contrast (Wet-SEEC) mode offers imaging and measurement of thin films at solid/liquid interfaces in the range 1–500 nm with lateral optical resolution. …
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Nano Lett, 2018

Optical magnetometry of single biocompatible micromagnets for quantitative magnetogenetic and magnetomechanical assays

Loïc Toraille, Koceila Aïzel, Elie Balloul, Chiara Vicario, Cornelia Monzel, Mathieu Coppey, Emilie Secret, Jean-Michel Siaugue, Joao Sampaio, Stanislas Rohart, Nicolas Vernier, Louise Bonnemay, Thierry Debuisschert, Loïc Rondin, Jean-Francois ROCH, and Maxime Dahan
The mechanical manipulation of magnetic nanoparticles is a powerful approach to probe and actuate biological processes in living systems. Implementing this technique in high-throughput assays can be achieved using biocompatible micomagnet arrays. Yet, the magnetic properties of these arrays are usually indirectly inferred from simulations or Stokes drag measurements, leaving unresolved questions about the actual profile of the magnetic fields at the micrometer scale and the exact magnetic forces that are applied. …
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BIORXIV, 2018

Extracellular matrix stiffness regulates force transmission pathways in multicellular ensembles of human airway smooth muscle cells.

Samuel R Polio, Suzanne Stasiak, Ramaswamy Krishnan, Harikrishnan Parameswaran
For an airway or a blood vessel to narrow, there must be a connected path that links the smooth muscle (SM) cells with each other, and transmits forces around the organ, causing it to constrict. Currently, we know very little about the mechanisms that regulate force transmission pathways in a multicellular SM ensemble. Here, we used extracellular matrix (ECM) micropatterning to study force transmission in a two-cell ensemble of SM cells. …
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BIORXIV, 2018

The cytoskeleton as a smart composite material: A unified pathway linking microtubules, myosin-II filaments and integrin adhesions

Nisha Mohd Rafiq, Yukako Nishimura, Sergey V. Plotnikov, Visalatchi Thiagarajan, Zhen Zhang, Meenubharathi Natarajan, Shidong Shi, Virgile Viasnoff, Gareth E. Jones, Pakorn Kanchanawong, Alexander D. Bershadsky
The interrelationship between microtubules and the actin cytoskeleton in mechanoregulation of integrin-mediated adhesions is poorly understood. Here, we show that the effects of microtubules on two major types of cell-matrix adhesions, focal adhesions and podosomes, are mediated by KANK family proteins connecting the adhesion protein talin with microtubule tips. Both total microtubule disruption and microtubule uncoupling from adhesions by manipulations with KANKs trigger a massive assembly of myosin-IIA filaments. …
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BIORXIV, 2018

A generic widefield topographical and chemical photopatterning method for hydrogels.

Aurelien Pasturel, Pierre-Olivier Strale, Vincent Studer
Physiologically relevant cell-based models require engineered microenvironments which recapitulate the topographical, biochemical and mechanical properties encountered in vivo. In this context hydrogels are the materials of choice. However, shaping hydrogels at the cellular scale and tuning their chemical properties requires deep investment in custom chemistry and devices while more accessible ones lack a simple structuration and functionalization mean. Here, we show how the most commonly used hydrogels (i.e. Matrigel, Agar, PEG, Polyacrylamide) can be finely structured and spatially functionalized by exploiting oxygen and radical photochemistry together with a widefield patterned UV light illumination. …
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Adv Biosys, 2018

A new approach to design artificial 3D micro-niches with combined chemical, topographical and rheological cues

Celine Stoecklin, Zhang Yue, Wilhelm W. Chen, Richard de Mets, Eileen Fong, Vincent Studer, Virgile Viasnoff
The in vitro methods to recapitulate environmental cues around cells are usually optimized to test a specific property of the environment (biochemical nature or the stiffness of the extra cellular matrix (ECM), or nanotopography) for its capability to induce defined cell behaviors (lineage commitment, migration). Approaches that combine different environmental cues in 3D to assess the biological response of cells to the spatial organization of different biophysical and biochemical cues are growingly being developed. …
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Lab Chip, 2018

In situ photopatterning of pressure-resistant hydrogel membranes with controlled permeabilities in PEGDA microfluidic channels.

Jérémy Decock, Mathias Schlenk and Jean-Baptiste Salmon
We report the fabrication of highly permeable membranes in poly(ethylene glycol) diacrylate (PEGDA) channels, for investigating ultra- or micro-filtration, at the microfluidic scale. More precisely, we used a maskless UV projection setup to photopattern PEG-based hydrogel membranes on a large scale (mm–cm), and with a spatial resolution of a few microns. We show that these membranes can withstand trans-membrane pressure drops of up to 7 bar without any leakage, thanks to the strong anchoring of the hydrogel to the channel walls. …
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BioRxiv, 2018

Collagen assembly and turnover imaged with a CRISPR-Cas9 engineered Dendra2 tag

Adam Pickard, Antony Adamson, Yinhui Lu, Joan Chang, Richa Garva, Nigel Hodson, Karl Kadler
Electron microscopy has been the gold standard for studying collagen networks but dynamic information on how cells synthesise the networks has been lacking. Live imaging methods have been unable to distinguish newly-synthesised fibrils from pre-existing fibrils and intracellular collagen. Here, we tagged endogenous collagen-I using CRISPR-Cas9 with photoswitchable Dendra2 and demonstrate live cells synthesising, migrating on, and interacting with, collagen fibrils. …
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Hum Mol Genet. 2016

Altered microtubule dynamics and vesicular transport in mouse and human MeCP2- deficient astrocytes.

Delépine C, Meziane H, Nectoux J, Opitz M, Smith AB, Ballatore C, Saillour Y, Bennaceur- Griscelli A, Chang Q, Williams EC, Dahan M, Duboin A, Billuart P, Herault Y, Bienvenu T.
Rett syndrome (RTT) is a rare X-linked neurodevelopmental disorder, characterized by normal post-natal development followed by a sudden deceleration in brain growth with progressive loss of acquired motor and language skills, stereotypic hand movements and severe cognitive impairment. Mutations in the methyl-CpG-binding protein 2 (MECP2) cause more than 95% of classic cases. …
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Adv Mater. 2016

Multiprotein Printing by Light-Induced Molecular Adsorption.

Strale PO, Azioune A, Bugnicourt G, Lecomte Y, Chahid M, Studer V.
Light-induced molecular adsorption of proteins (LIMAP) allows for quantitative sub-micrometer-resolution printing of multiple biomolecules. Surface-bound gradients are patterned within minutes over an entire glass cover-slip. LIMAP is used to perform selective immuno-assays, to dynamically control the adhesion of individual cells, and to achieve hierarchical co-cultures instrumental for tissue engineering.
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