Stromal cell-derived factor-1

SDF-1 (stromal cell-derived factor-1) is small cytokine belonging to the chemokine family that is officially designated Chemokine (C-X-C motif) ligand 12 (CXCL12).

Structure
SDF-1 is produced in two forms, SDF-1α/CXCL12a and SDF-1β/CXCL12b, by alternate splicing of the same gene. Chemokines are characterized by the presence of four conserved cysteines, which form two disulfide bonds. The CXCL12 proteins belong to the group of CXC chemokines, whose initial pair of cysteines are separated by one intervening amino acid.

Chemotaxis
CXCL12 is strongly chemotactic for lymphocytes.

During embryogenesis it directs the migration of hematopoietic cells from foetal liver to bone marrow and the formation of large blood vessels. Mice which were knocked-out for CXCL12 gene were lethal before the birth or within just 1 hour of life.

In adulthood CXCL12 plays an important role in angoigenesis by recruiting endothelial progenitor cells (EPC) from the bone morrow through a CXCR4 dependent mechanism. It is this function of CXCL12 that makes it a very important factor in carcinogenesis and the neovascularisation linked to tumour progression.

Electrophysiology
As another role, CXCL12a alters also the electrophysiology of neurons.

Others
CXCL12 was shown to be expressend in many tissues in mice (including brain, thymus, heart, lung, liver, kidney, spleen and bone marrow).

Receptor
The receptor for this chemokine is CXCR4, which was previously called fusin. This CXCL12-CXCR4 interaction used to be considered exclusive (unlike for other chemokines and their receptors), but recently it was suggested that CXCL12 is also bound by CXCR7 receptor.

Gene
The gene for CXCL12 is located on human chromosome 10. In human and mouse both CXCL12 and CXCR4 show high identity of sequence: 99% and 90%, respectively.