Revealing a role of microRNAs in the regulation of the biological clock

In the last decade numerous studies have unveiled the pervasive role of microRNAs (miRNAs), a class of small, non-coding transcripts, in post-transcriptional gene regulation in biological processes ranging from development to cancer. Until recently, the circadian clock has been modeled as simple, interlocking, transcriptional feedback loops that drive rhythmic gene expression of a few core 'clock' determinants. The biological implications of miRNAs are extended further by our recent discovery that miRNAs are expressed in the suprachiasmatic nuclei (SCN), the master circadian clock in mammals, in a rhythmic and inducible fashion, and modulate the intrinsic pacemaker activity and resetting capacity of the SCN. In this review, we will discuss the specific roles of miRNA-(miR-) 132 and miR-219 in the SCN, as well as a more general outlook on this newly elucidated layer of circadian clock regulation: inducible translation control via miRNAs.