Late endosome trafficking is slower in regenerated dendrites

Organelle trafficking is essential for neuronal function and homeostasis, particularly in dendrites where transport is required to maintain complex arbors. Following dendritic injury, extensive cellular reorganization occurs during regeneration, yet how this remodeling affects organelle transport dynamics remains poorly understood. To assess the consequences of regeneration on dendritic trafficking, we examined Rab7-labeled late endosome (LE) movement in class IV dendritic arborization neurons of Drosophila after dendrite injury. Using quantitative live imaging analysis, we found that retrograde LE trafficking speed is significantly reduced in regenerated dendrites compared to uninjured controls. However, anterograde LE trafficking speed, the directional bias of LE movement, the proportion of motile versus stationary organelles, LE number, and run length were not significantly different between uninjured versus regenerated neurons at either time point examined. These findings demonstrate that dendritic regeneration selectively impairs retrograde transport kinetics while preserving anterograde transport and directional control mechanisms. Regenerated dendrites are thinner than uninjured controls at early stages of regrowth but recover to normal caliber by later stages, yet retrograde transport deficits persist, suggesting caliber-independent regulation of retrograde transport speed. Our results suggest that altered organelle trafficking dynamics may represent a fundamental consequence of neuronal injury responses, with potential implications for understanding transport defects in regeneration after injury or disease involving dendritic damage.