Increased Levels of NOTCH1, NF-κB, and Other Interconnected Transcription Factors Characterize Primitive Sets of Hematopoietic Stem Cells
Stem Cells and Development
As previously shown, higher levels of NOTCH1 and increased NF-κB signaling is a distinctive feature of the more primitive umbilical cord blood (UCB) CD34+ hematopoietic stem cells (HSCs), as compared to bone marrow (BM). Differences between BM and UCB cell composition also account for this fi nding. The CD133 marker defi nes a more primitive cell subset among CD34+ HSC with a proposed hemangioblast potential. To further evaluate the molecular basis related to the more primitive characteristics
... ve characteristics of UCB and CD133+ HSC, immunomagnetically purifi ed human CD34+ and CD133+ cells from BM and UCB were used on gene expression microarrays studies. UCB CD34+ cells contained a signifi cantly higher proportion of CD133+ cells than BM (70% and 40%, respectively). Cluster analysis showed that BM CD133+ cells grouped with the UCB cells (CD133+ and CD34+) rather than to BM CD34+ cells. Compared with CD34+ cells, CD133+ had a higher expression of many transcription factors (TFs). Promoter analysis on all these TF genes revealed a signifi cantly higher frequency (than expected by chance) of NF-κB-binding sites (BS), including potentially novel NF-κB targets such as RUNX1, GATA3, and USF1. Selected transcripts of TF related to primitive hematopoiesis and self-renewal, such as RUNX1, GATA3, USF1, TAL1, HOXA9, HOXB4, NOTCH1, RELB, and NFKB2 were evaluated by real-time PCR and were all signifi cantly positively correlated. Taken together, our data indicate the existence of an interconnected transcriptional network characterized by higher levels of NOTCH1, NF-κB, and other important TFs on more primitive HSC sets.