Possible adhesion molecule with a role in early hematopoiesis by mediating the attachment of stem cells to the bone marrow extracellular matrix or directly to stromal cells. Could act as a scaffold for the attachment of lineage specific glycans, allowing stem cells to bind to lectins expressed by stromal cells or other marrow components. Presents carbohydrate ligands to selectins (By similarity). Expressed in the kidney where it is detected in the thin limb of Henle's loop (at protein level) (PubMed:31605441). Highly expressed in hematopoietic progenitor cell lines, brain and testis, and moderately in the thymus, spleen, and bone marrow, but not in adult liver (PubMed:1709048). Highly glycosylated. Phosphorylated on serine residues by PKC. Belongs to the CD34 family.