GATA2 Is Dispensable for Specification of Hemogenic Endothelium but Promotes Endothelial-to-Hematopoietic Transition.

Hyunjun Kang,Ho Sun Jung,Walatta-Tseyon Mesquitta,Igor I Slukvin,Oleg V Moskvin,James A Thomson

doi:10.1016/j.stemcr.2018.05.002

Abstract

SummaryThe transcriptional factor GATA2 is required for blood and hematopoietic stem cell formation during the hemogenic endothelium (HE) stage of development in the embryo. However, it is unclear if GATA2 controls HE lineage specification or if it solely regulates endothelial-to-hematopoietic transition (EHT). To address this problem, we innovated a unique system, which involved generating GATA2 knockout human embryonic stem cell (hESC) lines with conditional GATA2 expression (iG2−/− hESCs). We demonstrated that GATA2 activity is not required for VE-cadherin+CD43−CD73+ non-HE or VE-cadherin+CD43−CD73– HE generation and subsequent HE diversification into DLL4+ arterial and DLL4– non-arterial lineages. However, GATA2 is primarily needed for HE to undergo EHT. Forced expression of GATA2 in non-HE failed to induce blood formation. The lack of GATA2 requirement for generation of HE and non-HE indicates the critical role of GATA2-independent pathways in specification of these two distinct endothelial lineages.

Highlights

The formation of blood cells from hemogenic endothelium (HE) is a key element of embryogenesis leading to establishment of the hematopoietic system
It has become increasingly clear that HE represents a distinct subset of RUNX1-expressing CD73– vascular endothelium capable of undergoing endothelial-to-hematopoietic transition (EHT) (Choi et al, 2012; Ditadi et al, 2015; Jaffredo et al, 2010; North et al, 1999; Slukvin, 2016) and that hematopoietic specification occurs at the HE stage (Elcheva et al, 2014; Guibentif et al, 2017)
GATA2 transcription factor is of particular interest since it is critical for development of the entire hematopoietic system, including hematopoietic stem cells (HSCs) during embryogenesis

Summary

Introduction

The formation of blood cells from hemogenic endothelium (HE) is a key element of embryogenesis leading to establishment of the hematopoietic system. A number of transcription factors including RUNX1, GATA2, GFI1, HOXA3, SOX17, and TAL1, and NOTCH, WNT, and BMP/TGF-b signaling have been implicated in control of HE and blood development (reviewed in Slukvin, 2016; Swiers et al, 2013b; Thambyrajah et al, 2016b). GATA2 transcription factor is of particular interest since it is critical for development of the entire hematopoietic system, including hematopoietic stem cells (HSCs) during embryogenesis. GATA2 deficiency impairs hematopoiesis in mouse and human pluripotent stem cells (hPSC) cultures (Huang et al, 2015; Tsai and Orkin, 1997). Overexpression of GATA2 along with ETV2 or TAL1 in hPSCs directly induces HE with pan-myeloid or erythromegakaryocytic potentials (Elcheva et al, 2014)

Results

Discussion

Conclusion