Genome wide enrichment of H3.3 in WT and Hira-null embryonic stem cells and day 15 differentiated cardiac progenitor

HIRA is a histone chaperone that modulates gene expression through the deposition of H3.3. Conditional knockout of Hira in embryonic mouse hearts leads to cardiac septal defects. However, the effects of HIRA on the gene expression profile at earlier stages of cardiogenic mesoderm differentiation has not yet been studied. Differentiation of mouse embryonic stem cells (mESCs) towards cardiomyocytes mimics some of these events and is an accepted model of these early stages. We performed RNA-Seq and H3.3-HA ChIP-seq on both WT and Hira-null mESCs and early cardiomyocyte progenitors of both genotypes. Analysis of our RNA-seq data showed differential down regulation of cardiovascular development-related genes in Hira-null cardiomyocytes compared to WT cardiomyocytes. Correlating these data with H3.3 enrichment showed that HIRA is required for the expression of the transcription factors (TFs) Gata6, Meis1 and Tbx2. These TFs displayed diminished HIRA-dependent H3.3 enrichment in their gene bodies or at their transcription start site in the absence of HIRA. Our results reveal new transcription factors through which HIRA influences cardiogenesis in vitro and potentially in vivo. Genome wide enrichment of H3.3 in WT and Hira-null embryonic stem cells and day 15 differentiated cardiac progenitor.