Sialomucin that may play a key role in hematopoiesis by facilitating the adhesion of CD34(+) cells to the stroma and by negatively regulating CD34(+)CD38(lo/-) cell proliferation. Modulates the migration of umbilical cord blood CD133+ cells and this is mediated through the CXCL12/CXCR4 axis. May play an important role in prostate cancer metastasis and the infiltration of bone marrow by cancer cells. Promotes myogenesis by enhancing CXCR4-dependent cell motility. Positively regulates myoblast migration and promotes myoblast fusion into myotubes (By similarity). Homodimer (isoform 4). Interacts with CXCR4. Isoform 1 and isoform 3 are expressed in hematopoietic and non-hematopoietic tissues. Isoform 1 is expressed by prostate cancer tumors and prostate cancer cell lines. The expression is greater in bone metastases than in primary tumors. Expression in osseous metastasis is greater than that in soft tissue metastasis. Isoform 2 is expressed in the small intestine, colon, lung, thyroid and in colorectal and pancreatic adenocarcinoma. Isoform 4 is expressed by both hematopoietic progenitor cells and bone marrow stromal cells. Up-regulated by CXCL12 in prostate cancer cell lines. Highly N- and O-glycosylated; contains sialic acid. The motif Ser-Gly may serve as the site of attachment of a glycosaminoglycan side chain. The disease is caused by variants affecting the gene represented in this entry. Belongs to the CD164 family.