PROJECT SUMMARY Neurotransmitter release at synaptic terminals is tightly controlled, and its dysregulation has profound consequences for neural circuit activity and disease. Here, we propose to examine the in vivo impact of N6- methyladenosine (m6A), the most common internal modification of mRNA, on synaptic biology. Our ongoing efforts uncover how Drosophila mutants of m6A factors alter normal synaptic function at the neuromuscular junction (NMJ) and suggest new mechanisms for m6A regulation. We will build on this knowledge to dissect how m6A controls the ability of neurons to adjust their set point for neurotransmitter release at the synapse. This proposal will (1) establish critical roles for the epitranscriptome in normal synaptic function, (2) provide comprehensive genomic data on m6A targets and the regulatory impacts of these modifications, and (3) define new regulatory mechanisms by which m6A operates and intersects with other neuronal regulatory pathways. This work will provide conceptual advances to our knowledge of the regulation of neuronal activity under physiological conditions and in disease.