UTX in muscle regeneration--the right dose and the right time.

Precise epigenetic modifications in stem cells control developmental programs and cell fate decisions. In particular, the addition or removal of trimethylation of histone 3 lysine 27 (H3K27me3) at lineage-specific genes has been linked to the repression of gene expression, and a precise balance of methyltransferases and demethylases within cells determines H3K27me3 levels. The demethylase UTX is essential for development and tissue homeostasis; however, a role for UTX in stem cell-mediated tissue regeneration is unknown. In this issue of the JCI, Dilworth and colleagues reveal that UTX and its demethylase activity are required in the muscle stem cell lineage for muscle regeneration in response to injury. Specifically, UTX mediates the removal of H3K27me3 in the promoter of the transcription factor myogenin, which regulates myogenic differentiation. The results of this study provide important insight into the contribution of epigenetic regulation in stem cell-mediated regeneration of adult tissues.