Developmental regulation of endothelial-to-hematopoietic transition from induced pluripotent stem cells.

Hematopoietic stem cells (HSCs) arise in embryogenesis from a specialized hemogenic endothelium (HE) via endothelial-to-hematopoietic transition (EHT). While induced pluripotent stem cells (iPSCs) give rise to HE with robust hemogenic potential, bona fide HSC generation from iPSCs remains challenging. We map single-cell dynamics of EHT from iPSCs and integrate it with human embryo datasets to identify ligand-receptor interactions that drive transcriptional divergence between iPSC-derived and embryonic cell states. The expression of endothelial genes predicted to be regulated by FGF signaling was incompletely repressed during iPSC-derived EHT. FGF activity declined at the onset of EHT to enable normal hematopoiesis in the zebrafish, and chemical inhibition of FGF signaling during EHT enhanced HSC and progenitor generation in the zebrafish and from iPSCs. In summary, we generate a single-cell map of iPSC-derived EHT, identify ligand-receptor interactions that can improve iPSC differentiation, and uncover elevated FGF signaling as a barrier to hematopoiesis.