Scl specifies hemogenic endothelium and inhibits cardiogenesis via primed enhancers [ChIP-seq]
Scl/Tal1 confers hemogenic competence and prevents cardiomyogenesis in embryonic endothelium. Here we show that Scl both directly activates a broad gene regulatory network required for hematopoietic stem/progenitor cell (HS/PC) development, and represses transcriptional regulators required for cardiogenesis. Cardiac repression occurs during a short developmental window through Scl binding to distant cardiac enhancers that harbor H3K4me1 at this stage. Scl binding to hematopoietic regulators extends throughout HS/PC and erythroid development and spreads from distant enhancers to promoters. Surprisingly, Scl complex partners Gata 1 and 2 are dispensable for hematopoietic versus cardiac specification and Scl binding to the majority of its target genes. Nevertheless, Gata factors co-operate with Scl to activate selected transcription factors to facilitate HS/PC emergence from hemogenic endothelium. These results uncover a dual function for Scl in dictating hematopoietic versus cardiac fate choice and suggest a mechanism by which lineage-specific bHLH factors direct the divergence of competing fates. Overall design: ChIP-seq with Scl, Hand1, Lsd1, Ezh2, H3K4me1 and H3K27ac in different cell types with mesodermal origin. Scl ChIP-seq in WT, SclKO, SclKO-iScl and Gata12KO mES cell derived day4 EB (embryoid body) Flk1+ mesodermal cells, SclKO-iScl ES cells and MEL cells; Hand1 ChIP-seq in WT mES cell derived day4 EB Flk1+ mesodermal cells; Lsd1 and Ezh2 ChIP-seq in WT and SclKO mES cell derived day4 EB Flk1+ mesodermal cells. ChIP-seq of histone modifications H3K4me1 and H3K27ac in WT, SclKO and Gata12KO mES cell derived day4 EB Flk1+ mesodermal cells, HPC7 hematopoietic progenitor cells and HL1 cardiomyogenic cells