GSE130490
Context-dependent requirement of H3K9 dimethyltransferase activity during reprogramming to pluripotency
The methylation of histone 3 at lysine 9 (H3K9) is widely regarded as a major roadblock for cellular reprogramming and interference with associated methyltransferases such as EHMT1 and EHMT2 (also known as GLP and G9A) facilitates the derivation of induced pluripotent stem cells (iPSCs). In addition, activation of demethylases by ascorbic acid (AA) has become a common approach to facilitate the extensive epigenetic remodeling required for iPSC formation. The functional interaction between the H3K9 methylation machinery and AA-stimulated enzymes, and consequences of interfering with these pathways, remain insufficiently explored. Here, we show that reduction of EHMT1/2 activity paradoxically counteracts iPSC formation in an optimized reprogramming system in the presence of AA. At the cellular and molecular level, EHMT1/2 activity is required for efficient downregulation of somatic genes and transition into an epithelial state. Genetic interference with the demethylase KDM3B partially rescues the adverse effect of EHMT1/2 inhibition on iPSC formation. Transient inhibition of EHMT1/2 during reprogramming yields iPSCs that fail to efficiently give rise to viable mice, suggesting persistent molecular defects in these cells. Together, our observations document a more nuanced function of H3K9 methyltransferases during iPSC formation and suggest that the balancing of AA-stimulated enzymes by EHMT1/2 is required for efficient and error-free reprogramming to pluripotency. Overall design: RNA-seq in MEF samples (in duplicates) and MEF undergoing reprogramming (in triplicates) after Dox induction of OSKM with or without the presence of C3 and or UNC