CXCL12 is expressed in many tissues in mice including brain, thymus, heart, lung, liver, kidney, spleen, and bone marrow. CXCL12 is strongly chemotactic for lymphocytes. During embryogenesis, it directs the migration of hematopoietic cells from fetal liver to bone marrow and the formation of large blood vessels. It has also been shown that CXCL12 signalling regulates the expression of CD20 on B cells. CXCL12 is also chemotactic for mesenchymal stem cells and is expressed in the area of inflammatory bone destruction, where it mediates their suppressive effect on osteoclastogenesis.