MicroRNAs (miRNAs), prominent types of small noncoding RNA, have been revealed as key regulators of gene expression at the post-transcriptional level. Major advances in the understanding of miRNA biology in the past decades include biogenesis pathways, principles of target gene regulation and identification of target transcripts. Of note, miRNAs can act as a switch or a fine-tuner to control the level and function of target genes, which reciprocally regulate miRNAs via miRNA response elements at 3′ untranslated regions. In addition to current knowledge about miRNA biogenesis and function, this review looks at mounting evidence that aberrant expression of miRNAs in both the cerebral cortex and peripheral blood mononuclear cells may underlie many of the molecular changes observed in psychiatric disorders.
