The murine msh-like homeobox-containing gene Msx-2 (Hox-8) has a multiphasic pattern of embryonic expression which includes the developing skull bones and teeth. In order to determine whether this gene might be expressed in adult mineralizing tissues, an adult human bone cell (osteoblastic) cDNA library was screened with a murine Msx-2 probe. One of the positive clones obtained was sequenced in full and shown to be highly homologous to the murine Msx-2 gene. Expression of this gene, MSX2, was studied in human bone-derived cells, where a low level of expression was detected which was greatly induced by stimulation with 1,25(OH)2D3. Little or no increase in expression was detected with retinoic acid or TPA stimulation. In cultures of skin fibroblasts no stimulation of expression with 1,25(OH)2D3 was detected. MSX2 is the first homeobox-containing gene to be shown to be regulated by 1,25(OH)2D3 and to be expressed in adult human bone cells. These results suggest a possible role for MSX2 in bone cell differentiation and/or calcium homeostasis.