Abstract
Activating mutations in fibroblast growth factor receptor 2 (FGFR2) cause several craniosynostosis syndromes by affecting the proliferation and differentiation of osteoblasts, which form the calvarial bones. Osteoblasts respond to FGF with increased proliferation and inhibition of differentiation. We analyzed the gene expression profiles of osteoblasts expressing FGFR2 activating mutations (C342Y or S252W) and found a striking down-regulation of the expression of many Wnt target genes and a concomitant induction of the transcription factor Sox2. Most of these changes could be reproduced by treatment of osteoblasts with exogenous FGF. Wnt signals promote osteoblast function and regulate bone mass. Sox2 is expressed in calvarial osteoblasts in vivo and we show that constitutive expression of Sox2 inhibits osteoblast differentiation and causes down-regulation of the expression of numerous Wnt target genes. Sox2 associates with beta-catenin in osteoblasts and can inhibit the activity of a Wnt responsive reporter plasmid through its COOH-terminal domain. Our results indicate that FGF signaling could control many aspects of osteoblast differentiation through induction of Sox2 and regulation of the Wnt-beta-catenin pathway.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Animals
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Cell Differentiation / physiology*
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Cell Line, Transformed
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Cytoskeletal Proteins / metabolism
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DNA-Binding Proteins / genetics
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DNA-Binding Proteins / metabolism*
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Down-Regulation / drug effects
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Down-Regulation / physiology
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Fibroblast Growth Factors / metabolism
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Fibroblast Growth Factors / pharmacology
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Gene Expression Regulation / drug effects
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Gene Expression Regulation, Developmental / physiology
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Genes, Reporter / physiology
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Intercellular Signaling Peptides and Proteins / metabolism*
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Mice
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Mutation / physiology
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Osteoblasts / cytology
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Osteoblasts / drug effects
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Osteoblasts / metabolism*
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Osteogenesis / drug effects
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Osteogenesis / physiology
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Protein Structure, Tertiary / physiology
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Receptor Protein-Tyrosine Kinases / genetics
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Receptor Protein-Tyrosine Kinases / metabolism*
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Receptor, Fibroblast Growth Factor, Type 2
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Receptors, Fibroblast Growth Factor / genetics
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Receptors, Fibroblast Growth Factor / metabolism*
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SOXB1 Transcription Factors
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Signal Transduction / drug effects
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Signal Transduction / physiology
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Skull / abnormalities
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Skull / cytology
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Skull / metabolism
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Synostosis / genetics
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Synostosis / metabolism
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Synostosis / physiopathology
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Trans-Activators / genetics
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Trans-Activators / metabolism*
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Transcription Factors / genetics
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Transcription Factors / metabolism*
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Transcriptional Activation
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Wnt Proteins
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beta Catenin
Substances
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CTNNB1 protein, mouse
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Cytoskeletal Proteins
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DNA-Binding Proteins
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Intercellular Signaling Peptides and Proteins
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Receptors, Fibroblast Growth Factor
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SOXB1 Transcription Factors
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Sox2 protein, mouse
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Trans-Activators
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Transcription Factors
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Wnt Proteins
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beta Catenin
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Fibroblast Growth Factors
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Fgfr2 protein, mouse
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Receptor Protein-Tyrosine Kinases
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Receptor, Fibroblast Growth Factor, Type 2