Osteoclast Stimulatory Transmembrane Protein (OCSTAMP)

Osteoclast stimulatory transmembrane protein and dendritic cell–specific transmembrane protein cooperatively modulate cell–cell fusion to form osteoclasts and foreign body giant cells. Cell–cell fusion is a dynamic phenomenon promoting cytoskeletal reorganization and phenotypic changes. OC-STAMP–deficient mice exhibited a complete lack of cell–cell fusion of osteoclasts and foreign body giant cells (FBGCs), both of which are macrophage-lineage multinuclear cells, although expression of dendritic cell specific transmembrane protein (DC-STAMP), which is also essential for osteoclast/FBGC fusion, was normal. Crossing OC-STAMP–overexpressing transgenic mice with OC-STAMP–deficient mice restored inhibited osteoclast and FBGC cell–cell fusion seen in OC-STAMP–deficient mice.