Hematopoietic stem cell markers and their potential signaling interactions governing their biology. A schematic diagram of potential signaling pathways downstream of key markers expressed on CD34⁺(CD38/CD45RA)^–EPCR⁺ HSCs (which are also CD49f⁺ and CD90⁺/⁻) upon interacting with their potential ligands in the niche. This highly HSC-enriched population highly expresses CD33, CD93, CD117, CD133, and CD143.³⁰ We hypothesize that these cells may also express GPRC5C and CD370 as well as PAR1 and ATR1 (to convey the EPCR/APC/PAR1 and CD143/Ang-/ATR1 signaling, respectively).