The long noncoding RNA scaffolds neuronal granules to maintain nervous system maturity.

RNA binding proteins and messenger RNAs (mRNAs) assemble into ribonucleoprotein granules that regulate mRNA trafficking, local translation, and turnover. The dysregulation of RNA-protein condensation disturbs synaptic plasticity and neuron survival and has been widely associated with human neurological disease. Neuronal granules are thought to condense around particular proteins that dictate the identity and composition of each granule type. Here, we show in that a previously uncharacterized long noncoding RNA, , is required to scaffold large neuronal granules in the adult nervous system. Neuronal ELAV-like proteins directly bind and mediate granule assembly, while Staufen maintains condensate integrity. granules contain mRNAs and proteins involved in synaptic processes; granule loss in mutant flies impairs nervous system maturity and neuropeptide-mediated signaling and causes phenotypes of neurodegeneration. Our work reports an architectural RNA for a neuronal granule and provides a handle to interrogate functions of a condensate independently of those of its constituent proteins.