The Circular RNA Edis Regulates Neurodevelopment and Innate Immunity

Circular RNAs (circRNAs) are widely expressed in eukaryotes. However, only a subset have been functionally characterized. We identify and validate a collection of circRNAs in Drosophila, and show that depletion of the brain-enriched circRNA Edis causes hyperactivation of antibacterial innate immunity both in cultured cells and in vivo. Notably, Edis depleted flies display heightened resistance to bacterial infection and enhanced pathogen clearance. Conversely, ectopic Edis expression blocks innate immunity signaling. In addition, inactivation of Edis in vivo leads to impaired locomotive activity and shortened lifespan. Remarkably, these phenotypes can be recapitulated with neuron-specific depletion of Edis, accompanied by defective neurodevelopment. Importantly, restoration of Edis expression suppresses both innate immunity and neurodevelopment phenotypes elicited by Edis depletion. We provide evidence that Edis encodes a functional protein that associates with and compromises the processing of the immune transcription factor Relish. Consistent with these observations, inactivation of Relish suppresses the innate immunity hyperactivation phenotype in the fly brain and rescues the neurodevelopment defects in Edis knockdown neurons. Thus, our study establishes the circRNA Edis as a key regulator of neurodevelopment and innate immunity. Identification of circular RNAs in cultured Drosophila S2 cells.