Analysis of phase separation at the synapse:
How to transfer in vitro data to an intact synapse?
Liquid-liquid phase separation (LLPS) has been implicated by in vitro studies in the organization of synaptic vesicle clusters, but it has remained unclear whether this applies to in vivo conditions.
Liquid-liquid phase separation (LLPS) is an increasingly recognized mechanism for compartmentalization in cells. Recent in vitro studies suggest that this organizational principle may apply to synaptic vesicle clusters. Here we test this possibility by performing microinjections at the living lamprey giant reticulospinal synapse. Axons were maintained at rest to examine if reagents introduced into the cytosol would enter a putative liquid phase to disrupt critical protein-protein interactions. We found that compounds that perturb the intrinsically disordered region of synapsin, which is critical for liquid phase organization in vitro, cause dispersion of synaptic vesicles from resting clusters.