Dopamine neuron specific RNA-sequencing reveals Neprilysin 1 acts downstream of the cohesin complex to suppress learning

We previously identified Stromalin, a cohesin complex subunit, as a learning suppressor in Drosophila melanogaster that acts by limiting synaptic vesicle numbers in dopamine neurons. However, the mechanism by which Stromalin modulates synaptic vesicles remains unclear. We hypothesized that this occurred through the cohesin complex's function in developmental gene regulation. Through dopamine neuron-specific RNA-sequencing followed by RNAi screening, we identified Neprilysin 1 (Nep1), a zinc-dependent metallopeptidase, to be positively regulated by the cohesin complex and a key downstream effector of Stromalin. Nep1 knockdown phenocopies Stromalin knockdown effects, enhancing learning and memory and increasing synaptic vesicle markers in dopamine neurons. Like Stromalin, Nep1 suppresses synaptic strength between dopamine and mushroom body neurons. Finally, we show Nep1 overexpression rescues both memory and synaptic vesicle phenotypes caused by Stromalin reduction. Interestingly, while cohesin complex appears to set the expression levels for Nep1 during development, Nep1 function in adult flies supports its learning effects.