Wetting-Mediated Remodeling of the Cytoskeletal Cortex by Phase-Separated Condensates in Cell-Free Reactions

Living cells dynamically coordinate gene expression with the spatial organization of their membranes and cytoskeletons. Unraveling how membrane-less organelles arise and interact with cytoskeletal networks remains a fundamental challenge in cell biology, biophysics, and bioengineering. Here, we present a synthetic biology platform that integrates cell-free transcription-translation (TXTL) reactions with phase-separated protein condensates, enabling precise investigation of their interplay with cytoskeletal elements. We show that the bacterial actin homologue MreB forms a scaffold that promotes the wetting of protein condensates in crowded solutions, triggering capillary-driven contraction of the cytoskeletal network. Remarkably, MreB filaments self-assemble into a cortical layer at water-oil droplet interfaces, where their contractile activity leads to wrinkling and global deformation of the synthetic compartment. Our results provide physical insights into how biomolecular condensates and cytoskeletal filaments cooperate to remodel cell-like structures, and establish a minimal model for studying wetting-mediated cytoskeletal dynamics at synthetic membranes.