Raphaël Clément (Institut de Biologie du Développement de Marseille). Mechanics of cell contacts during embryonic morphogenesis.

During animal development, tissue shape changes can be achieved by the local generation of active cellular forces. Measuring these forces and understanding how they are converted into cell and tissue deformation is essential to our understanding of embryonic morphogenesis.

I will present an experimental analysis of how cell contacts in the Drosophila embryo respond to forces, both endogenous (Myosin motors) or applied externally (optical tweezers). The response is consistent with a simple viscoelastic model. Interestingly, the timescale of dissipation is commensurate with that of endogenous force generation, which allows efficient remodelling of cell contacts during morphogenesis. We also show that the turnover of Actin filaments, by renewing the mechanical structure of the cell, participates in dissipation and therefore affects the reversibility of morphogenetic deformations. Overall our results argue that tissue morphogenesis requires coordination between force generation and internal dissipation.

I will also present, in a variety of in vivo tissues, how solving an inverse mechanics problem allows inferring tensions at cell contacts and tissue level stresses from a single image.