Figure 3

Model for circuits involving Polycomb Group (PcG) proteins and miRNAs during muscle cell differentiation. In blue: in differentiating myoblasts, miR-29b2/miR-29c, miR-214 and miR-26a are induced by muscle-specific transcription factors, such as MyoD and MEF2, and post-transcriptionally block the expression of YY1 and EZH2 PcG proteins. Together with the inhibition of HDAC4 expression by miR-1, these phenomena lead to differentiation of myogenic precursor cells. In red: in the absence of a differentiative stimulus, YY1 and EZH2 are highly expressed and foster the proliferation (i.e., expansion) of progenitor cells by repressing the expression of miR-29 and miR-214 and down-regulating muscle-specific genes.