Guiding growing droplets through the cytoskeleton

Phase-separation of biomolecules in cells takes place in a complex environment crossed by multiple filaments of the cytoskeleton or chromatin. Previous studies of artificial droplets forming inside a polymer gel have identified mechanisms that lead to a finite droplet size and even induce motion of droplets through gradients in network stiffness. Here, we study the interactions of stress granules, a phase-separated protein-RNA droplet in the cytosol, with the heterogeneous networks of actin and microtubules. Introducing a radial distribution function for disordered and finite systems such as a cell, we identify different interactions between stress granule and actin and microtubules giving rise to directed motion and final arrest of the droplet in microtubule rich locations.