Single-cell transcriptomics identifies CD44 as a marker and regulator of endothelial to haematopoietic transition

Abstract

The endothelial to haematopoietic transition (EHT) is the process whereby haemogenic endothelium differentiates into haematopoietic stem and progenitor cells (HSPCs). The intermediary steps of this process are unclear, in particular the identity of endothelial cells that give rise to HSPCs is unknown. Using single-cell transcriptome analysis and antibody screening, we identify CD44 as a marker of EHT enabling us to isolate robustly the different stages of EHT in the aorta-gonad-mesonephros (AGM) region. This allows us to provide a detailed phenotypical and transcriptional profile of CD44-positive arterial endothelial cells from which HSPCs emerge. They are characterized with high expression of genes related to Notch signalling, TGFbeta/BMP antagonists, a downregulation of genes related to glycolysis and the TCA cycle, and a lower rate of cell cycle. Moreover, we demonstrate that by inhibiting the interaction between CD44 and its ligand hyaluronan, we can block EHT, identifying an additional regulator of HSPC development.

Multi-layered Spatial Transcriptomics Identify Secretory Factors Promoting Human Hematopoietic Stem Cell Development

“…Combined transcriptome analysis revealed many other secreted factors that would be worth exploring further. One such example is SPP1, which has a documented role in the fetal and adult bone marrow, modulating HSC proliferation and migration (Nilsson et al, 2005;Cao et al, 2019;Stier et al, 2005), and binds CD44, recently implicated in EHT (Luo et al, 2011;Oatley et al, 2020). Our population and single-cell analysis showed that SPP1 is mainly generated by hematopoietic populations, perhaps by macrophages (Lund et al, 2009).…”

Hematopoietic stem cells from pluripotent stem cells: Clinical potential, challenges, and future perspectives

“…Currently, known cell surface markers to distinguish primitive/definitive hematopoiesis are similar; therefore, identifying globin profiles in RBCs and lymphoid potential of HSC‐like cells from PSCs are the generally applied methods. To improve this, for instance, a recent report demonstrated CD44 as a novel cell surface marker for HSC‐primed HE cells in the AGM region 79 . Besides, hepatic leukemia factor ( Hlf ) expression was recently reported as a discriminating factor for mouse liver HSCs from EMPs or hematopoietic clusters in the yolk sac (E9) 80 .…”

Location, Location, Location: How Vascular Specialization Influences Hematopoietic Fates During Development

“…hyaluronic acid) was recently shown to influence hematopoietic development in the AGM via its receptor CD44. Although CD44 is known to influence homing and migration of hematopoietic stem/progenitor cells (HSPCs) to the bone marrow in adults (Schmits et al, 1997;Avigdor et al, 2004), its role in early HSC development in the AGM was only recently revealed (Oatley et al, 2020). Utilizing antibody screening and singlecell molecular analyses, it was discovered that CD44 expression is upregulated in a subset of arterial ECs transitioning from HE to HSCs and progenitors in the AGM.…”

“…Utilizing antibody screening and singlecell molecular analyses, it was discovered that CD44 expression is upregulated in a subset of arterial ECs transitioning from HE to HSCs and progenitors in the AGM. Interestingly, CD44 appears to be a driver, not simply a marker, of the endothelial to hematopoietic transition, as disruption of hyaluronan binding to CD44, via antibody blockage or inhibition of hyaluronan synthesis, reduces hematopoietic production from HE (Oatley et al, 2020). Although the source of hyaluronan production within the AGM is not yet defined, previous studies have shown that proinflammatory stimuli can regulate the endothelial cell production of hyaluronan in vivo and in vitro (Mohamadzadeh et al, 1998;Vigetti et al, 2010), suggesting that a similar mechanism may regulate its production within the AGM.…”