Identification and characterization of a synaptic active zone assembly protein

At presynaptic active zones (AZs), scaffold proteins play a crucial role in coordinating synaptic vesicle (SV) release and forming intricate nanoarchitectures essential for synaptic function. Despite their suspected importance, factors governing the assembly of nanoscale AZ scaffolds have remained elusive. Here, we identify "Blobby" as a novel regulator of AZ nanopatterning, localized within the AZ scaffold. Genetic loss of the extended Blobby protein led to aberrant accumulation of AZ scaffold proteins ("blobs") and disrupted the nanoscale architecture of the AZ scaffold, resulting in a significant reduction in the packing density of voltage-gated Ca2+ channels at AZs, as observed through intravital single-molecule imaging. This disruption correlated with decreased evoked synaptic currents and SV release probability. Our findings suggest that Blobby plays a crucial role in switching the AZ scaffold into a state which allows to fine-tune the dynamic nanopatterning of Ca2+ channels to maintain proper release.