CD27 marks embryonic hematopoietic stem cells

Cell surface markers of adult hematopoietic stem cells (HSCs) are well established, but fewer markers are available for embryonic HSCs and their immediate precursors (pre-HSCs) in the major arteries. We performed RNA-Seq on a population of cells from the major arteries of embryonic day 11.5 mouse embryos enriched for lymphoid progenitors, pre-HSCs, and HSCs. We determined that Tnfrsf7, encoding CD27, a member of the tumor necrosis factor receptor superfamily, is upregulated in this population. CD27 is found on ~5% of hematopoietic cluster cells in the major arteries, and enriches for progenitors with lymphoid potential, embryonic HSCs, and Type II pre-HSCs (CD144+CD45+), and fetal liver HSCs. It does not, however, enrich for yolk sac derived erythro-myeloid progenitors. Collectively, those data show that CD27 is a new cell surface marker of embryonic HSCs and Type II pre-HSCs. Overall design: Major arteries in dorsal aorta, umbilical, vitelline (A+U+V) from 122 embryonic day 11.5 Ly6a-GFP+ embryos were dissected and disaggregated with collagenase, and 53,000 Ly6a-GFP+ hematopoietic cluster cells (CD31+ CD144+ ESAM+ c-Kit+), 413,000 Ly6a-GFP- hematopoietic cluster cells, 377,000 Ly6a-GFP+ endothelial cells (CD31+ CD144+ ESAM+ c-Kit-), and 791,000 Ly6a-GFP- endothelial cells collected. Cells were sorted into TRIzol-LS (Invitrogen) and pooled into three independent biological samples. The cells were lysed in TRIzol-LS and the aqueous phase was collected after adding chloroform. The aqueous phase was homogenized by 70% ethanol and RNA isolated using Qiagen RNeasy micro kit. Isolated RNA was treated with TURBO DNA-free DNA Removal Kit to remove contaminating DNA.