Illuminating microRNA Transcription from the Epigenome.

Cellular gene expression is governed by a complex, multi-faceted network of regulatory interactions. In the last decade, microRNAs (miRNAs) have emerged as critical components of this network. miRNAs are small, non-coding RNA molecules that serve as post-transcriptional regulators of gene expression. Although there has been substantive progress in our understanding of miRNA-mediated gene regulation, the mechanisms that control the expression of the miRNAs themselves are less well understood. Identifying the factors that control miRNA expression will be critical for further characterizing miRNA function in normal physiology and pathobiology. We describe recent progress in the efforts to map genomic regions that control miRNA transcription (such as promoters). In particular, we highlight the utility of large-scale "-omic" data, such as those made available by the ENCODE and the NIH Roadmap Epigenomics consortiums, for the discovery of transcriptional control elements that govern miRNA expression. Finally, we discuss how integrative analysis of complementary genetic datasets, such as the NHGRI Genome Wide Association Studies Catalog, can predict novel roles for transcriptional mis-regulation of miRNAs in complex disease etiology.