Since we have shown that Nrp2 is a direct vitamin D target gene, we aimed to investigate whether treatment with the vitamin D analog WY 1048, which is able to prevent bone loss in an ovariectomy-induced model of osteoporosis (22), increases bone mass to the same extent in osteoblast-specific Nrp2 knockout mice as in their wildtype littermates. The gene discussed is NRP2; the disease is osteoporosis.