CD34 is a type I transmembrane glycosylated phosphoprotein expressed by hematopoietic stem/progenitor cells (HSPCs), vascular endothelial cells, and some fibroblastic cells. For many years, CD34 expression has been utilized as a key marker for identifying and isolating hematopoietic stem cells. Upon stimulation with cytokines or growth factors, CD34+ hematopoietic stem cells expand and differentiate into various lympho-hematopoietic lineages, subsequently losing CD34 expression during this process. However, recent studies from different laboratories have presented findings that contradict this conventional paradigm. The extracellular domain of CD34 exhibits homology with CD43, a protein implicated in intercellular adhesion, and CD34 itself has been demonstrated to function as a negative regulator of cell adhesion. CD34 interacts with CrkL but not with CrkII. CrkII is a substrate for protein kinase C (PKC), and PKC activation is coupled to the surface expression of CD34.
i_FC_04.jpg?t=1767197014)
