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. 2014 Jun 10;289(31):21533–21543. doi: 10.1074/jbc.M113.543330

FIGURE 6.

FIGURE 6.

The in vivo working model. a, DMP1 secreted from the cell binds to integrin via its RGD domain, followed by activation of the MAP kinase signaling pathway (27, 29). The targeted expression of DMP1 in the nucleus has no direct role in osteogenesis in vivo. b, DMP1 expressed in the osteoblast (Ob) facilitates cell proliferation and transformation (from osteoblasts into osteocytes (Ocy)). Deletion of Dmp1 leads to an increase in cell proliferation and a reduction in osteoblast cell differentiation. Because of the great increase of FGF23 in Dmp1-KO osteocytes, the reduced Pi causes an increase in cell proliferation and differentiation in chondrocytes (a new indirect role of hypophosphatemia in the growth plate), in addition to the abnormality in the apoptosis pathway (46).