Abstract
A limited set of cell-cell signaling pathways presides over the vast majority of animal developmental events. The typical raison d'etre for signal transduction is to control the transcription of protein-coding genes. However, with the recent appreciation of microRNAs, growing attention has been paid towards understanding how signaling pathways intertwine with microRNA-mediated regulation. This review highlights recent studies that uncover unexpected modes of microRNA regulation by cell signaling pathways. Not only can miRNA transcription be positively or negatively regulated by cell signaling, the TGF-β/BMP pathways and Ras/MAPK pathways have now been shown to directly influence microRNA biogenesis to mediate substantial cellular phenotypes.