Final Report Summary - BIOFIB (Disordered assemblies of biofilaments: from aggregation to contractility)
The first system we consider is disordered assemblies of actin filaments and molecular motors that contract in vivo. These systems self-organize to induce cell motility according to different mechanisms than ordered structures, and we have compared these non-conventional mechanisms and determined which one dominates their activity. This problem crucially involves the mesoscopic structure of the filament assembly, which we also considered. Going beyond existing naive equilibrium models, this second study focused on the out-of-equilibrium competition between filament growth and aggregation, which experiments have recently shown to dominate actin gel structure. We have developed models of this process in the reaction-limited and diffusion-limited regimes. Finally, we questioned the foundations of these two first studies by asking why protein filaments are so abundant; indeed, they form even in situations where their presence harms the cell. Consistent with this we have shown that in a specific model protein-like particles have a natural tendency towards filament formation, which relieves the geometrical frustration resulting from their ill-fitting shapes.
The fellow has a permanent position at CNRS and has been successfully building his own research group since the beginning of the project, obtaining an ERC Starting Grant, the IUPAP Young Scientist Award for Statistical Physics and an EMBO Young Investigator Award.