pyrophosphate and Craniosynostoses

One diagnostic feature of craniosynostosis syndromes is mandibular dysgenesis. Using three mouse models of Apert, Crouzon and Pfeiffer craniosynostosis syndromes, we investigated how embryonic development of the mandible is affected by fibroblast growth factor receptor 2 (

Topics: Animals; Cell Proliferation; Chondrocytes; Craniosynostoses; Diphosphates; Disease Models, Animal; Embryo, Mammalian; Mandible; Mice; Models, Biological; Osteoblasts; Osteogenesis; Receptor, Fibroblast Growth Factor, Type 2

Fibroblast growth factor/fibroblast growth factor receptor (FGF/FGFR) signaling is associated with the aberrant mineralization phenotype of the craniosynostosis syndromes. One critical aspect of mineralization involves the elaboration and transport of pyrophosphate into the extracellular matrix with subsequent enzymatic hydrolysis into phosphate. We have previously shown that FGF2 up-regulates expression of the pyrophosphate generating enzyme, PC-1, and the pyrophosphate channel, ANK, while down-regulating expression of the pyrophosphate hydrolyzing enzyme, tissue non-specific alkaline phosphatase in pre-osteoblastic, MC3T3E1(C4) cells. These results suggest that FGF/FGFR signaling may affect mineralization via changes in the elaboration and metabolism of pyrophosphate.. We are currently conducting experiments towards a more systematic analysis of PC-1 expression in osteoblastic cells, in order to more clearly elucidate the significance of pyrophosphate elaboration in the process of normal bone mineralization and in the molecular etiology of the FGFR-associated craniosynostosis syndromes.. Towards this goal we have constructed a PC-1 gene promoter/firefly luciferase reporter construct, in order to more directly investigate the regulation of PC-1 by FGF/FGFR signaling in osteoblastic and non-osteoblastic cells.. Preliminary results confirm that FGF/FGFR signaling, either via treatment with FGF2 or via expression of a Crouzon syndrome-associated mutant FGFR2, induces PC-1 promoter activity in osteoblastic cells in culture. This appears to be a cell type specific phenomenon. These results suggest that the expression of PC-1 downstream of FGF signaling is an integral aspect of osteoblastic function, and that pyrophosphate elaboration may play a significant role in the pathology of craniosynostosis.

Topics: 3T3 Cells; Animals; Calcification, Physiologic; Craniosynostoses; Diphosphates; Fibroblast Growth Factor 2; Gene Expression Regulation, Developmental; Genes, Reporter; Luciferases, Firefly; Mice; Osteoblasts; Phosphoric Diester Hydrolases; Promoter Regions, Genetic; Pyrophosphatases; Receptor, Fibroblast Growth Factor, Type 2; Signal Transduction; Up-Regulation

Fibroblast growth factor/fibroblast growth factor receptor (FGF/FGFR) signaling has been linked to the aberrant mineralization phenotype of craniosynostosis syndromes. One critical aspect of mineralization involves the elaboration and transport of pyrophosphate into the extracellular matrix with subsequent enzymatic hydrolysis into phosphate. Altered expression of the pyrophosphate elaborating factors, TNAP (tissue nonspecific alkaline phosphatase), PC-1, and ANK, downstream of FGF/FGFR signaling may provide a potential mechanism for the craniosynostosis phenotype. As an initial step toward testing this hypothesis, we confirmed that ANK mRNA is upregulated during osteoblast differentiation in culture. Subsequently, the effect of FGF2 treatment on expression of PC-1, ANK, and TNAP in the calvarial osteoblastic cell line, MC3T3E1(C4), was investigated. FGF2 specifically induced expression of PC-1 and ANK while inhibiting expression of TNAP, at both mRNA and protein levels. Concordant with these changes in gene expression, FGF2 inhibited mineralization. These results suggest that FGF/FGFR signaling may affect mineralization via changes in the elaboration and metabolism of pyrophosphate.

Topics: Alkaline Phosphatase; Animals; Calcification, Physiologic; Cell Differentiation; Cell Line; Craniosynostoses; Diphosphates; Fibroblast Growth Factor 2; Gene Expression Regulation, Developmental; Membrane Proteins; Mice; Osteoblasts; Phosphate Transport Proteins; Phosphates; Phosphoric Diester Hydrolases; Pyrophosphatases; Receptors, Fibroblast Growth Factor; RNA, Messenger; Signal Transduction; Skull; Up-Regulation

Topics: Craniosynostoses; Diphosphates; Humans; Infant; Radiography; Radionuclide Imaging; Skull; Technetium; Time Factors