Inhibition of miRNA-212/132 improves the reprogramming of fibroblasts into induced pluripotent stem cells by de-repressing important epigenetic remodelling factors.

MicroRNAs (miRNAs) repeatedly have been demonstrated to play important roles in the generation of induced pluripotent stem cells (iPSCs). To further elucidate the molecular mechanisms underlying transcription factor-mediated reprogramming we have established a model, which allows for the efficient screening of whole libraries of miRNAs modulating the generation of iPSCs from murine embryonic fibroblasts. Applying this model, we identified 14 miRNAs effectively inhibiting iPSC generation, including miR-132 and miR-212. Intriguingly, repression of these miRNAs during iPSC generation also resulted in significantly increased reprogramming efficacy. MiRNA target evaluation by qRT-PCR, Western blot, and luciferase assays revealed two crucial epigenetic regulators, the histone acetyl transferase p300 as well as the H3K4 demethylase Jarid1a (KDM5a) to be directly targeted by both miRNAs. Moreover, we demonstrated that siRNA-mediated knockdown of either p300 or Jarid1a recapitulated the miRNA effects and led to a significant decrease in reprogramming efficiency. Thus, conducting a full library miRNA screen we here describe a miRNA family, which markedly reduces generation of iPSC and upon inhibition in turn enhances reprogramming. These miRNAs, at least in part, exert their functions through repression of the epigenetic modulators p300 and Jarid1a, highlighting these two molecules as an endogenous epigenetic roadblock during iPSC generation.