Abstract.:

 

Actomyosin is one of the components of the constantly remodelling skeleton of living cells. Two out-of-equilibrium phenomena confer it intriguing mechanical properties: turnover, thanks to which the network can grow by polymerisation at its boundaries while it depolymerises in denser regions, and contractility, which allows it to generate internal tensile stress. I will show using simple models some basic properties of actomyosin in extremely simple geometries. Then I will show that, when interacting with an elastic foundation, actomyosin turnover can induce a breaking of symmetry that entails persistent motion. This instability is likely to play a role in the spontaneous polarisation and initiation of migration of living cells cultured on a deformable substrate.