Defining the roles of ETV2 in human hematopoiesis in vitro

Abstract

The deep understanding of hematopoiesis would improve the strategy for hematopoietic stem cell (HSC) generation from pluripotent stem cells (PSCs). Several studies in animal model have indicated Etv2 as a master regulator in hematopoietic and vascular development. Moreover, Etv2 might be essential for HSCs generation. To study roles of ETV2 during human hematopoietic development in vitro, we used embryonic stem cell-derived sacs (ES-sac) as a model of hematopoietic development in which the steps of hematopoiesis could be visualized. ETV2 reporter iPSC line (ETV2:GFP iPSCs) was generated to track ETV2 expression during the development. We found that hemato-vascular mesoderm (HVM) were generated and given rise to hematopoietic lineage in which might be inducted by ETV2. Moreover, ETV2:GFP expressing mesoderm failed to contribute to cardiac cells, thus implying the inhibition of cardiac fate of mesoderm progenitor. After ETV2 was upregulated during mesodermal specification then downregulated, ETV2 was upregulated again, the second wave, in hemogenic endothelium (HE) in later ES-sac. On the second wave, expression of ETV2 correlated with expression of RUNX1C, a HSCs markers. Additionally, ETV2 expressing KIT+CD235a- HE population in later ES-sac expressed levels of SOX17, a marker of HE in aorta-gonad-mesonephros (AGM), higher than early one, indicating the ETV2:GFP+KIT+CD235a- HE might become more similar to a definitive hematopoietic cell in the AGM. In conclusions, our studies in human hematopoietic development in vitro support the notion ETV2 might play an essential role in HSCs generation.