UMR168 – Laboratoire Physico-Chimie Curie

Publications de l’UMR 168

Année de publication : 2018

Vincent Nier, Grégoire Peyret, Joseph d'Alessandro, Shuji Ishihara, Benoit Ladoux, Philippe Marcq (2018 Oct 11)

Kalman Inversion Stress Microscopy.

Biophysical journal : DOI : S0006-3495(18)31065-8 En savoir plus

Although mechanical cues are crucial to tissue morphogenesis and development, the tissue mechanical stress field remains poorly characterized. Given traction force time-lapse movies, as obtained by traction force microscopy of in vitro cellular sheets, we show that the tissue stress field can be estimated by Kalman filtering. After validation using numerical data, we apply Kalman inversion stress microscopy to experimental data. We combine the inferred stress field with velocity and cell-shape measurements to quantify the rheology of epithelial cell monolayers in physiological conditions, found to be close to that of an elastic and active material.

Duclos G., Blanch-Mercader C., Yashunsky V., Salbreux G., Joanny J.-F., Prost J., Silberzan P. (2018 Oct 3)

Spontaneous shear flow in confined cellular nematics

Nature Physics : DOI : 10.1038/s41567-018-0099-7 En savoir plus

In embryonic development or tumour evolution, cells often migrate collectively within confining tracks defined by their microenvironment1,2. In some of these situations, the displacements within a cell strand are antiparallel3, giving rise to shear flows. However, the mechanisms underlying these spontaneous flows remain poorly understood. Here, we show that an ensemble of spindle-shaped cells plated in a well-defined stripe spontaneously develops a shear flow whose characteristics depend on the width of the stripe. On wide stripes, the cells self-organize in a nematic phase with a director at a well-defined angle with the stripe’s direction, and develop a shear flow close to the stripe’s edges. However, on stripes narrower than a critical width, the cells perfectly align with the stripe’s direction and the net flow vanishes. A hydrodynamic active gel theory provides an understanding of these observations and identifies the transition between the non-flowing phase oriented along the stripe and the tilted phase exhibiting shear flow as a Fréedericksz transition driven by the activity of the cells. This physical theory is grounded in the active nature of the cells and based on symmetries and conservation laws, providing a generic mechanism to interpret in vivo antiparallel cell displacements.

Merle T, Farge E. (2018 Aug 1)

Trans-scale mechanotransductive cascade of biochemical and biomechanical patterning in embryonic development: the light side of the force.

Curr. Opin. Cell. Biol. : DOI : 10.1016/ En savoir plus

Embryonic development is made of complex tissue shape changes and cell differentiation tissue patterning. Both types of morphogenetic processes, respectively biomechanical and biochemical in nature, were historically long considered as disconnected. Evidences of the biochemical patterning control of morphogenesis accumulated during the last 3 decades. Recently, new data revealed reversal mechanotransductive feedback demonstrating the strong coupling between embryonic biomechanical and biochemical patterning. Here we will review the findings of the emerging field of mechanotransduction in animal developmental biology and its most recent advancements. We will see how such mechanotransductive cascade of biochemical and mechanical patterning events ensures trans-scale direct cues of co-regulation of the microscopic biomolecular activities with the macroscopic morphological patterning. Mechanotransduction regulates many aspects of embryonic development including efficient collective cell behaviour, distant tissues morphogenesis coordination, and the robust coordination of tissue shape morphogenesis with differentiation.

Röper Jens-Christian, Mitrossilis Démosthène, Stirnemann Guillaume, Waharte François, Brito Isabel, Fernandez-Sanchez Maria-Elena, Baaden Marc, Salamero Jean, Farge Emmanuel (2018 Jul 19)

The major β-catenin/E-cadherin junctional binding site is a primary molecular mechano-transductor of differentiation in vivo

eLIFE : 7:e33381. DOI: : DOI : DOI: En savoir plus

In vivo, the primary molecular mechanotransductive events mechanically initiating cell differentiation remain unknown. Here we find the molecular stretching of the highly conserved Y654-beta-catenin-D665-E-cadherin binding site as mechanically induced by tissue strain. It triggers the increase of accessibility of the Y654 site, target of the Src42A kinase phosphorylation leading to irreversible unbinding. Molecular dynamics simulations of the beta-catenin/E-cadherin complex under a force mimicking a 6 pN physiological mechanical strain predict a local 45% stretching between the two a-helices linked by the site and a 15% increase in accessibility of the phosphorylation site. Both are quantitatively observed using FRET lifetime imaging and non-phospho Y654 specific antibody labelling, in response to the mechanical strains developed by endogenous and magnetically mimicked early mesoderm invagination of gastrulating Drosophila embryos. This is followed by the predicted release of 16% of beta-catenin from junctions, observed in FRAP, which initiates the mechanical activation of the b-catenin pathway process.