The transcription factor Sox9 is involved in BMP-2 signaling.
We investigated the regulation of Sox9, a transcription factor known to play a role in chondrogenesis, by bone morphogenetic protein-2 (BMP-2) and hedgehog proteins in order to better understand their signaling function in endochondral bone formation. The mesenchymal progenitor cell line C3H10T1/2 was stimulated with BMP-2. Sox9 expression levels were measured by quantitative reverse transcriptase-polymerase chain reaction and Northern analysis. We found that Sox9 was up-regulated by BMP-2 in a dose-dependent manner. The expression of Col2a1, a downstream response gene of Sox9, was also significantly increased upon BMP-2 addition. We also monitored Sox9 expression after the addition of BMP-2 to osteosarcoma cell lines; BMP-2 treatment increased Sox9 mRNA levels in MG63, considered to be early osteoblast-like, but not in human osteogenic sarcoma (HOS) cells, which are thought to be more advanced in the osteoblastic lineage. This response seems to be influenced by differences in BMP receptor expression; MG63 cells express BMP receptor IA (BMPR-IA), whereas HOS cells express BMPR-IA and BMPR-IB. We also saw an increase in Sox9 mRNA levels in BMP-2-treated primary human bone cells (HBCs) derived from femoral heads. We found that in addition to BMP-2, Sonic and Indian hedgehog can increase Sox9 expression in C3H10T1/2 and primary HBCs. Time course studies with C3H10T1/2 cells after BMP-2 stimulation showed increasing expression of cartilage markers, decrease of collagen I mRNA, and a late induction of osteocalcin expression. Moreover, the treatment of C3H10T1/2 cells with Sox9 antisense oligonucleotides revealed that Sox9 is a downstream mediator of BMP-2 affecting the expression of chondrocyte and osteoblast marker genes. Our data show that Sox9 is an important downstream mediator of the BMP-2 and hedgehog signaling pathways in osteogenic cells.
Zehentner
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BK
Roche Pharmaceuticals, Molecular Biology, Roche Diagnostics, GmbH, Penzberg, Germany.
Dony
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C
Burtscher
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D000818:Animals; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000502:physiology*; D002478:Cells, Cultured; D020219:Chondrogenesis / Q000502:physiology*; D006609:High Mobility Group Proteins / Q000502:physiology*; D006801:Humans; D051379:Mice; D020133:Reverse Transcriptase Polymerase Chain Reaction; D055758:SOX9 Transcription Factor; D015398:Signal Transduction / Q000502:physiology*; D014157:Transcription Factors / Q000502:physiology*; D016212:Transforming Growth Factor beta; D014407:Tumor Cells, Cultured
C525718:BMP2 protein, human; C525719:Bmp2 protein, mouse; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D006609:High Mobility Group Proteins; D055758:SOX9 Transcription Factor; C527932:SOX9 protein, human; C527933:Sox9 protein, mouse; D014157:Transcription Factors; D016212:Transforming Growth Factor beta