Speaker: Prof. Jocelyn Etienne

Abstract

Morphogenesis is a three-dimensional process during which an organism undergoes complex deformations to acquire a given shape and organisation. The genetic patterning of embryos and the way this regulates key molecules and complexes, such as actomyosin, is well described. How the molecular motor Myosin II generates local mechanical action is understood, however, the way this is integrated at the scale of the embryo to drive cell-scale deformations and, at a larger scale, morphogenetic movements is still to be characterised.
In a first part, I will show how one can derive a model of active gel for actomyosin from a mechanistic point of view. I will briefly show how this model behaves in simple one dimensional setups. Then, I will show that this model also captures the essential phenomena happening at the tissue scale. Axis extension in Drosophila is a good model system for this, since it involves the deformation of the whole of the embryonic epithelium. It is dependent on a well-characterised anisotropic myosin recruitement pattern in the germband tissue, where actomyosin organises in oriented supracellular cables through a planar-polarisation mechanism. Finally, I will go back to a smaller spatial scale and investigate the link between our understanding of the subcellular dynamics of actomyosin and the global morphogenetic behaviour.

Biography

An applied mathematics graduate, I have focused on the numerical resolution of complex fluid flow problems in my PhD and post-doc. My PhD (2004) was set within a collaboration between an applied mathematics lab, now LJK Grenoble, and a fluid mechanics one, LEGI Grenoble. With Pierre Saramito and Emil Hopfinger, we focused on gravity-driven flows of mixtures of very large density ratios, and specifically powder-snow avalanches. My post-doc at the University of Cambridge was part of an industry-oriented project on inkjet printing technologies. With John Hinch, I focused on the breakup of jets of polymeric liquids. I have joined CNRS in 2007 at what is now LIPHY Grenoble to investigate the mechanics of the cytoskeleton. Focusing on actomyosin, I have developed collaborations with experimentalists who investigate its role in the mechanics of biological material both at the cell scale and at the tissue scale.