A nanoscale atlas of extracellular vesicles and particles in Drosophila olfactory sensilla

Abstract

Extracellular particles, including non-vesicular extracellular particles (NVEPs) and extracellular vesicles (EVs), are emerging as key contributors to sensory signaling, yet their ultrastructural organization within native tissues remains underexplored. Native tissues preserve extracellular particle organization and heterogeneity that are often lost during dissociation. Using cryofixation-based serial block-face scanning electron microscopy, we generated a nanoscale atlas of NVEPs and EVs across 352 Drosophila antennal olfactory sensilla ([~]70% coverage). Segmentation of more than 7,800 extracellular particles revealed distinct populations differing in morphology, size, electron density, and sensillum-class distribution. Analyses of EV biogenesis identified multivesicular bodies and membrane budding in auxiliary cells. Furthermore, sensilla housing degenerating neurons exhibited marked accumulation of EVs and NVEPs, accompanied by increased auxiliary-cell EV biogenesis. Together, these findings provide a large-scale ultrastructural characterization of extracellular particles in native sensory tissues and establish a foundation for understanding how extracellular particles are distributed, generated, and function during sensory signaling and degeneration.