SOX17 integrates HOXA and arterial programs in hemogenic endothelium to drive definitive lympho-myeloid hematopoiesis

Ho Sun Jung,Gene Uenishi,Mi Ae Park,Peng Liu,Kran Suknuntha,Matthew Raymond,Yoon Jung Choi,James A Thomson,Irene M Ong,Igor I Slukvin

doi:10.1016/j.celrep.2021.108758

Abstract

SUMMARYSOX17 has been implicated in arterial specification and the maintenance of hematopoietic stem cells (HSCs) in the murine embryo. However, knowledge about molecular pathways and stage-specific effects of SOX17 in humans remains limited. Here, using SOX17-knockout and SOX17-inducible human pluripotent stem cells (hPSCs), paired with molecular profiling studies, we reveal that SOX17 is a master regulator of HOXA and arterial programs in hemogenic endothelium (HE) and is required for the specification of HE with robust lympho-myeloid potential and DLL4+CXCR4+ phenotype resembling arterial HE at the sites of HSC emergence. Along with the activation of NOTCH signaling, SOX17 directly activates CDX2 expression, leading to the upregulation of the HOXA cluster genes. Since deficiencies in HOXA and NOTCH signaling contribute to the impaired in vivo engraftment of hPSC-derived hematopoietic cells, the identification of SOX17 as a key regulator linking arterial and HOXA programs in HE may help to program HSC fate from hPSCs.

Highlights

SOX17 knockout impairs arterial-type HE (AHE) specification and definitive lympho-myeloid hematopoiesis from human pluripotent stem cells (hPSCs) To assess the effect of SOX17 on hematopoietic development, we generated SOX17 knockout H9 human embryonic stem cell (hESC) (SOX17À/À) lines using CRISPR/Cas9 (Figures S1A–S1C) and differentiated them into endothelial and hematopoietic cells in a chemically defined culture system (Uenishi et al, 2014)
The primitive hematopoietic progenitors (HPs) with fibroblast growth factor 2 (FGF2)-dependent hemangioblast (HB)-colony-forming cell (CFC) potential are detected on day 3 of differentiation (Choi et al, 2012; Uenishi et al, 2014; Vodyanik et al, 2010)
Evaluation of day 4 cultures revealed that SOX17 knockout had minimal effect on day 4 hemogenic endothelium (HE); analysis of day 5 cultures showed significantly impaired the specification of DLL4+CXCR4+ AHE when compared to wild-type H9 hESCs (Figures 1C–1E)

Summary

Introduction

Sox has been found to be expressed in the arterial vasculature (Liao et al, 2009) and the hemogenic endothelium (HE) in the aorta-gonad-mesonephros (AGM) region (Clarke et al, 2013; Corada et al, 2013), in which it is required for arterial specification (Corada et al, 2013) and essential for establishing the definitive, but not primitive, hematopoietic program (Clarke et al, 2013) within the murine embryo. Transduction of human embryonic stem cell (hESC)-derived CD34+ HE/OP9 cocultures with a tamoxifen-inducible murine Sox transgene revealed that tamoxifen treatment expands CD34+CD43+CD45À/low cells coexpressing the endothelial marker VE-cadherin (VEC) (Nakajima-Takagi et al, 2013). No activation of the NOTCH pathway following Sox overexpression was observed during hESC differentiation (Nakajima-Takagi et al, 2013) While these studies established an important role for SOX17 in the specification of definitive hematopoiesis and its diverse effects on EHT and HSCs, the molecular program induced by SOX17 at distinct stages of hematopoietic development, especially in humans, remains poorly understood

Results

Discussion

Conclusion