Proceedings of The Nice Spring School on M odelling C omplex B iological S ystems in the C ontext of G enomics March 30 th - April 3 rd , 2009

I give a survey of the work which we have done over the last years on ”active gels”. In particular, I show how one can construct a set of equations describing gels in which the cross-links can be moved around by active elements constantly consuming energy. This situation corresponds to the cell cytoskeleton, which is thought to control most of cell dynamics. We illustrate the potential usefulness of the equations by discussing cell behavior such as motility, oscillations, wound healing and cytokinesis. Eventually, I discuss tissue growth, introducing the concept of homeostatic pressure and tumor nucleation.