Dynamics and mechanics of actin cytoskeleton networks in vitro and in cellulo*

Actin is a protein which self-assembles into highly dynamic filaments organized, within the cells, in different kinds of structures: bundled, crosslinked, contractile or branched networks. Actin interacts with a large number of partners either regulating the meshwork dynamics (polymerization, depolymerization and contractility) or the meshwork architecture (bundling, branching or crosslinking proteins). The architecture dictates the mechanics of the network and combines to its dynamic properties to enable the cell to achieve essential processes like migration, deformation or integration of external signals. I will show in this talk how we take advantage of the self-assembly of magnetic micro-particles to study simultaneously dynamic and mechanical properties of different actin networks. Results on actin cortex directly in living cells as well as on in vitro Arp2/3 actin networks resembling the ones at play in lamellipodia or in endocytosis will be discussed.