Regulation of miR-219 and its target RalGPS is essential for synaptic plasticity at the Drosophila neuromuscular junction.

miR-219–target RalGPS regulation is essential for activity-induced structural synaptic plasticity at Drosophila glutamatergic synapses, with both RalGPS loss and excess abolishing synapse growth.

• Why it matters: Adaptive structural remodeling at synapses depends on rapid RNA regulatory control, but how miRNA loading into Ago1 complexes tunes plasticity is unclear.
• What they did: In Drosophila glutamatergic synapses, acute stimulation downregulates miRNA targets including RalGPS; RalGPS expression range was tested, and stimulation effects on miR-219 loading in Ago1 complexes were measured.
• The result: Stimulation elevates miR-219 loading in Ago1-containing complexes without changing mature miR-219, while elevated Protein Kinase A suppresses miR-219–Ago1 association and blocks activity-induced synaptic growth.