AUD-associated mRNA expression changes can only partially explain the molecular mechanisms of AUD. Noncoding RNAs, particularly small noncoding microRNAs (miRNAs), have drawn much attention as they are potent and multifunctional regulators of many biological processes. miRNAs are a class of about 22 nucleotide-long small noncoding RNAs that act as regulators of gene expression at the post-transcriptional level. They bind to the 3′ untranslated region (3′ UTR) of their target mRNAs, resulting in either mRNA degradation (when their sequences are perfectly matched) or translational inhibition (when their sequences are imperfectly matched) [16]. The function of miRNAs implies an additional layer of gene expression regulation besides genetic variation. Accumulating evidence suggests that alcohol could induce miRNA expression changes, leading to altered cellular functions. Expression changes in miRNAs and their target mRNAs have been demonstrated as a consequence of exposure of alcohol to cultured cells [17, 18] as well as mouse [19] and rat [20–23] brains. miRNA transcriptomic changes have also been observed in postmortem PFC [13, 24] and NAc [15] of AUD subjects by microarray-based transcriptome analysis.
