Genetic dissection of the

Neuronal trafficking pathways must operate with high fidelity and speed, adapting to the dynamic demands of synaptic activity to maintain stable functionality. The Biogenesis of Lysosome-Related Organelles Complex 1 (BLOC-1) is an attractive candidate to stabilize synaptic function during such challenges. BLOC-1 is an evolutionarily conserved protein complex composed of eight subunits involved in vesicle trafficking. In the nervous system, the BLOC-1 is associated with neurodevelopmental diseases and synaptic plasticity. However, the functions of each BLOC-1 component remain enigmatic. Here, we use CRISPR to mutate each Drosophila BLOC-1 gene to investigate roles in synaptic growth, function, and homeostatic plasticity. First, we show that BLOC-1 mutations are viable, with no defects in synaptic growth, morphology, or baseline function. We then demonstrate distinct synaptic localization patterns of BLOC-1 components. Finally, we show that only two of the eight BLOC-1 components, dysbindin and snapin, are necessary for presynaptic homeostatic potentiation. These results indicate separable functions and distinct synaptic localization patterns of BLOC-1 subunits, and a need to reconsider predictions made from biochemical models of BLOC-1.