Cécile Sykes (Institut Curie,Paris). ENS-ESPCI Biophysics Seminar

17 March 2017 13:00 » 14:00 — ENS, Room L374/L376 3rd floor

Tension build-up in cells and in biomimetic systems

Cell tension plays a crucial role in many biological processes; in particular, acto-myosin cortical tension drives many events of cell fate, including cell division. The tension of a cell is defined by analogy with the surface tension of a liquid droplet: the energy one has to pay to increase the drop, or cell, area. It was hypothesized by ME Terret and MH Verlhac at Collège de France that cell tension may have a role in the geometry of cell division that relies exclusively on actin. In this context, we characterized cell tension in their mouse oocytes and one-cell embryos (called zygote). Mouse oocytes undergo a very asymmetric division in size during meiosis I, whereas one-cell embryos divide symmetrically. We measured cell tension and could validate their hypothesis that the specific cortical actin structure connected to an actin cytoplasmic meshwork did, indeed, control the geometry of cell division. We find that the geometry of division, in particular on and an actin cage that surrounds the microtubule spindle. In order to unveil generic mechanisms of cell movements and shape changes, our team designs stripped-down experimental systems that reproduce cellular behaviours in simplified conditions, using liposome membranes on which cytoskeleton dynamics are reconstituted. Such stripped-down systems allow for a controlled study of the physical mechanisms that underlie cell movements and cell shape changes. Moreover, these experimental systems are used to address biological issues within a controlled, simplified environment. We have reconstituted the actin cortex of cells at the membrane of liposomes, and characterized their mechanical properties. We will show how these cortices contract in the presence of myosin motors, and how such experiments shed light of the mechanisms of cell shape changes.