TGF-β Regulates miR-206 and miR-29 to Control Myogenic Differentiation through Regulation of HDAC4

MicroRNAs (miRs) are emerging as prominent players in the regulation of many biological processes, including myogenic commitment and skeletal muscle formation. Members of the TGF-beta family can influence the proliferation and myogenic differentiation of cells, although it is presently not clear what role miRNAs play in the TGF-beta-mediated control of myogenic differentiation. Here, we demonstrate in the myogenic C2C12 cell line, and in primary muscle cells, that miR-206 and miR-29-two miRs that act on transcriptional events implicated in muscle differentiation are down-regulated by TGF-beta. We further demonstrate that TGF-beta treatment of myogenic cells is associated with increased expression of histone deacetylase 4 (HDAC4), a key inhibitor of muscle differentiation that has been identified as a target for regulation by miR-206 and miR-29. We confirmed that increased expression of miR-206 and miR-29 resulted in the translational repression of HDAC4 in the presence or absence of TGF-beta via interaction with the HDAC4 3'-untranslated region. Importantly, we found that miR-206 and miR-29 can attenuate the inhibitory actions of TGF-beta on myogenic differentiation. Furthermore, we present evidence that the mechanism by which miR-206 and miR-29 can inhibit the TGF-beta-mediated up-regulation of HDAC4 is via the inhibition of Smad3 expression, a transducer of TGF-beta signaling. These findings identify a novel mechanism of interaction between TGF-beta and miR-206 and -29 in the regulation of myogenic differentiation through HDAC4.