Putative membrane receptor for 1,25(OH)2 vitamin D3 in human mineralized tissues during prenatal development

The calciotropic hormone, 1,25(OH)2vitamin D3[1,25(OH)2D3], controls the formation of dental and bone mineralized tissues. The role of nuclear 1,25(OH)2D3 receptor has been extensively studied in the diverse secretory cells, i.e., osteoblasts, chondrocytes, ameloblasts, and odontoblasts. A nongenomic pathway also has been characterized and related to the interactions of 1,25(OH)2D3 ligand with a putative cell membrane receptor. This recognition moiety called 1,25(OH)2vitamin D3 membrane-associated, rapid-response steroid-binding [1,25D3-MARRS] protein is investigated here in the craniofacial skeleton of human embryos and fetuses. Immunolocalization using a specific Ab099 against chick intestinal basolateral 1,25D3-MARRS protein was performed. The data show a complementary expression pattern of the membrane receptor when compared with published data on the nuclear receptor, notably during amelogenesis. In mandible, membrane receptors for 1,25(OH)2D3 were identified in the heterogenous bone cell population, including osteoblasts and osteoclasts. Differential 1,25D3-MARRS protein levels were observed in distinct developmental stages and anatomical sites of tooth and bone, suggesting the existence of cross-talk between local factors and 1,25D3-MARRS protein expression.