Abstract
Mouse embryonic fibroblasts (MEFs) can be differentiated into fully functional chondrocytes in response to bone morphogenetic protein-2 (BMP-2). The expression of Sox9, a critical transcription factor for the multiple steps of chondrogenesis, has been reported to be upregulated during this process. But the molecular mechanisms by which BMP-2 promotes chondrogenesis still remain largely unknown. The aim of the present study was therefore to investigate the underlying mechanism. In the MEFs, BMP-2 efficiently induced Sox9 expression along with chondrogenic differentiation in a time- and dose-dependent manner. SB203580, a specific inhibitor for p38 pathway, blocked BMP-2-induced chondrogenic differentiation as well as Sox9 expression and its transactivation of downstream genes. Forced expression of Smad6, a natural antagonist for BMP/Smad pathway, only inhibited Sox9 protein function without rendering any effects on its mRNA expression. A CCAAT box was identified in Sox9 promoter as the cis-elements responsible for BMP-2 stimulation. This study provides insight into the mechanisms underlying BMP-2-regulated Sox9 expression and activity in MEFs, and suggests differential roles of BMP-2/p38 and BMP-2/Smad pathways in modulating the function of Sox9 during chondrogenesis.
(c) 2008 Wiley-Liss, Inc.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Base Sequence
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Blotting, Western
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Bone Morphogenetic Protein 2
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Bone Morphogenetic Proteins / metabolism*
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Cell Differentiation / physiology
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Cells, Cultured
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Chickens
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Chondrogenesis / physiology*
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Electrophoretic Mobility Shift Assay
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Enzyme Activation / physiology
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Enzyme Inhibitors / pharmacology
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Fibroblasts / cytology*
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Gene Expression Regulation*
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High Mobility Group Proteins / genetics
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High Mobility Group Proteins / metabolism*
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Humans
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Mice
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Mice, Inbred BALB C
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Molecular Sequence Data
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Promoter Regions, Genetic
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Reverse Transcriptase Polymerase Chain Reaction
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SOX9 Transcription Factor
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Sequence Homology, Nucleic Acid
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Smad6 Protein / metabolism
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Transcription Factors / genetics
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Transcription Factors / metabolism*
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Transfection
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Transforming Growth Factor beta / metabolism*
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p38 Mitogen-Activated Protein Kinases / drug effects
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p38 Mitogen-Activated Protein Kinases / metabolism
Substances
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BMP2 protein, human
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Bmp2 protein, mouse
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Bmp2 protein, rat
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Bone Morphogenetic Protein 2
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Bone Morphogenetic Proteins
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Enzyme Inhibitors
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High Mobility Group Proteins
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SOX9 Transcription Factor
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SOX9 protein, human
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Smad6 Protein
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Smad6 protein, rat
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Sox9 protein, mouse
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Transcription Factors
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Transforming Growth Factor beta
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p38 Mitogen-Activated Protein Kinases