MiR-92 Controls Synaptic Development Through Glial Vha55 Regulation.

MicroRNAs (miRNAs) have emerged as important biomarkers for complex neurological conditions. Modifications in synaptic morphology characterize several of these disease states, indicating a possible role of miRNA in modulating synaptic formation and plasticity. Within the third-instar larvae of Drosophila melanogaster, we uncovered a functional role for highly human-conserved miR-92 in synaptogenesis of the glutamatergic peripheral nervous system. Loss of miR-92 results in underdeveloped synaptic architecture, coinciding with significantly reduced physiological activity. We demonstrate a novel role for miR-92 glial-specific expression to support synaptic growth function and plasticity. Modifications of miR-92 within glial tissue result in aberrant glial barrier properties, including an increased uptake of external dyes. Within the glia, miR-92 regulates a V-ATPase subunit (Vha55), impairing the glial cells from forming appropriate insulating layers around the nervous system. These modifications may impact how the nervous system adapts to its environment, increasing immature 'ghost bouton' budding and impairing responses to changes in environmental conditions. Our work highlights the importance of glial-specific miR-92 on synaptic development, affecting glial health and function through its downstream target Vha55, and demonstrates a novel mechanism for glia in synaptogenesis and homeostatic plasticity.