Here we show that m6A modification on miRNAs (i) impairs their function on target mRNAs, (ii) determines their extracellular delivery into extracellular vesicles (EVs) and (iii) provides functional information to receiving cells.
RNA modification, frequently referred as epitranscriptomics, is emerging as a new layer of gene expression regulation. In particular, the most frequent internal mRNA modification, the addition of a methyl group to carbon 6 of adenosine (m6A), regulates RNA maturation, stability, degradation and translation. With respect to miRNAs, while it has been reported that m6A impact their biogenesis, no evidence is as yet provided on m6A role on their function. Here we show that m6A modification on miRNAs (i) impairs their function on target mRNAs, (ii) determines their extracellular delivery into extracellular vesicles (EVs) and (iii) provides functional information to receiving cells. The causal mechanisms for these phenomena are: (i) the intracellular functional impairment is caused by m6A-mediated inhibition of AGO2/miRNA interaction (ii) the EV loading is favoured by m6A-mediated recognition by the sequence specific RNA binding protein hnRNPA2B1 (iii) the EV-miRNAs function in the receiving cell require their demethylation mediated by FTO demethylase.  As a consequence, cells express specific miRNAs that do not impact endogenous transcripts but provide instead regulatory information for cell-to-cell communication and m6A modification contributes to miRNA cargo loading into EVs. This highlights that a further level of complexity should be considered when relating cellular differentiation and plasticity in pathophysiology to specific repertoire of miRNAs.