Genome-wide maps of Super-enhancers in TH9 cells by H3K27Ac and BRD4 CHIP-Seq.

Th cell differentiation is transcriptionally regulated, relying on the induction of “lineage-defining” transcription factors. We report that formation of super-enhancers is critical in robust induction of Th9 cells and that assembly of the Il9 super-enhancers requires OX40-triggered chromatin H3K27 acetylation. Mechanistically, we found that OX40 costimulation induces RelB expression, which recruits the histone acetyltransferase p300 to the Il9 locus to catalyze H3K27 acetylation. This allows binding of the super-enhancer factor Brd4 to initiate assembly of the super-enhancer complex, which in turn drives robust Th9 induction. Thus, Th9 cells are induced in massive numbers upon OX40 costimulation and disruption of super-enhancers abolished Th9 induction in vitro and inhibited Th9-mediated allergic airway inflammation in vivo. Our data identify super-enhancers as a key mechanism of Th9 induction and uncover a new mechanism of Th cell differentiation. Overall design: Analysis of H3K27Ac histone modifications and BRD4 binding in CD4+ T cells cultured in vitro under Th9 differentiation conditions for 48 hours in the presence or absence of OX40 ligation.