Axonal precursor miRNAs hitchhike on endosomes and locally regulate the development of neural circuits
Eloina Corradi, Irene Dalla Costa, Antoneta Gavoci, Archana Iyer, Michela Roccuzzo, Tegan A. Otto, Eleonora Oliani, Simone Bridi, Stephanie Strohbuecker, Gabriela Santos‐Rodriguez, Donatella Valdembri, Guido Serini, Cei Abreu‐Goodger, Marie‐Laure Baudet
Abstract
Various species of non‐coding RNAs (ncRNAs) are enriched in specific subcellular compartments, but the mechanisms orchestrating their localization and their local functions remain largely unknown. We investigated both aspects using the elongating retinal ganglion cell axon and its tip, the growth cone, as models. We reveal that specific endogenous precursor microRNAs (pre‐miRNAs) are actively trafficked to distal axons by hitchhiking primarily on late endosomes/lysosomes. Upon exposure to the axon guidance cue semaphorin 3A (Sema3A), pre‐miRNAs are processed specifically within axons into newly generated miRNAs, one of which, in turn, silences the basal translation of tubulin beta 3 class III (TUBB3), but not amyloid beta precursor protein (APP). At the organismal level, these mature miRNAs are required for growth cone steering and a fully functional visual system. Overall, our results uncover a novel mode of ncRNA transport from one cytosolic compartment to another within polarized cells. They also reveal that newly generated miRNAs are critical components of a ncRNA‐based signaling pathway that transduces environmental signals into the structural remodeling of subcellular compartments. Mechanisms regulating subcellular localization and local function of non‐coding RNA are not well understood. Here, neuronal pre‐miRNAs are found to traffic along axons docked to endosomes, with axonal processing of pre‐miRNAs leading to the inhibition of local protein synthesis. Pre‐miRNAs transported to distal axons are locally processed upon exposure to Sema3A and are required for growth cone steering and a fully functional visual system.