Promotes osteogenesis by stimulating the differentiation of mesenchymal progenitors into mature osteoblasts. Important for repair and maintenance of adult bone. Detected in femur where it localizes to trabecular bone of the femur metaphysis, and cortical bone of the proximal femur. Also expressed in trabecular and cortical bone of vertebrae (at protein level). Strongly expressed in osteoblasts and bone marrow stromal cells. Also has very weak expression in B cell progenitors in the bone marrow and T cells in the spleen. O-glycosylated. Probably sulfated on the O-glycans (By similarity). Viable with no gross defects. Trabecular bone volume and bone mineral density is significantly reduced at two months of age, and progressively worsens with age. Bone strength is reduced and fracture healing is impaired. Hematopoiesis appears to be normal. Stem cell growth factor