GATA2^(−/−) human ESCs undergo attenuatedendothelial to hematopoietic transition andthereafter granulocyte commitment

Background: Hematopoiesis is a progressive process collectively controlled by an elaborate network of transcriptionfactors (TFs). Among these TFs, GATA2 has been implicated to be critical for regulating multiple steps of hematopoiesisin mouse models. However, whether similar function of GATA2 is conserved in human hematopoiesis, especially duringearly embryonic development stage, is largely unknown.Results: To examine the role of GATA2 in human background, we generated homozygous GATA2 knockout humanembryonic stem cells (GATA2^(−/−) hESCs) and analyzed their blood differentiation potential. Our results demonstratedthat GATA2^(−/−) hESCs displayed attenuated generation of CD34^(+)CD43^(+) hematopoietic progenitor cells (HPCs), due tothe impairment of endothelial to hematopoietic transition (EHT). Interestingly, GATA2^(−/−) hESCs retained the potentialto generate erythroblasts and macrophages, but never granulocytes. We further identified that SPI1 downregulationwas partially responsible for the defects of GATA2^(−/−) hESCs in generation of CD34^(+)CD43^(+) HPCs and granulocytes.Furthermore, we found that GATA2^(−/−) hESCs restored the granulocyte potential in the presence of Notch signaling.Conclusion: Our findings revealed the essential roles of GATA2 in EHT and granulocyte development throughregulating SPI1, and uncovered a role of Notch signaling in granulocyte generation during hematopoiesis modeled byhuman ESCs.