Intimate relationship between TGF-beta/BMP signaling and runt domain transcription factor, PEBP2/CBF.
BACKGROUND
When C2C12 pluripotent mesenchymal precursor cells are treated with transforming growth factor-beta1 (TGF-beta1), terminal differentiation into myotubes is blocked. Treatment with bone morphogenetic protein-2 (BMP-2) not only blocks myogenic differentiation but also induces osteoblastic differentiation. However, the molecular mechanisms governing the ability of TGF-beta and BMP to induce ligand-specific responses and inhibit myogenic differentiation are not known. The objective of our studies was to elucidate the molecular mechanisms that block myoblastic differentiation and induce osteoblastic differentiation in C2C12 cells.


METHODS
Induction of RUNX2/PEBP2alphaA/Cbfa1 by TGF-beta and BMP was examined by electrophoretic mobility shift assay (EMSA) and Northern blot analysis. C2C12 cells stably expressing RUNX2 or Smad, or both, were established, and the role of these genes in the process of osteoblastic differentiation was analyzed by examining the expression of osteoblast-specific markers.


RESULTS
Treatment of C2C12 with TGF-beta and BMP-induced RUNX2/PEBP2alphaA/Cbfa1, a global regulator of osteogenesis. Cooperation between RUNX2 and BMP-activated Smad induced osteoblastic differentiation.


CONCLUSIONS
Both TGF-beta and BMP activate transcription of RUNX2, which is sufficient to inhibit myogenesis. To induce osteogenesis, BMP-induced RUNX2 must cooperate with BMP-activated Smads.
Department of Biochemistry, School of Medicine, and Medical Research Institute, Chungbuk National University, Cheongju, Korea.
S C
SC
Bae
K S
KS
Lee
Y W
YW
Zhang
Y
Y
Ito
D000818:Animals; D019485:Bone Morphogenetic Proteins / Q000502:physiology*; D002478:Cells, Cultured; D050659:Core Binding Factor Alpha 1 Subunit; D050660:Core Binding Factors; D004268:DNA-Binding Proteins / Q000502:physiology*; D029721:Drosophila Proteins; D005786:Gene Expression Regulation / Q000502:physiology; D006801:Humans; D009363:Neoplasm Proteins; D015398:Signal Transduction / Q000502:physiology*; D051785:Smad Proteins; D015534:Trans-Activators / Q000502:physiology; D050656:Transcription Factor AP-2; D014157:Transcription Factors / Q000502:physiology*; D016212:Transforming Growth Factor beta / Q000502:physiology*
C105841:Bgb protein, Drosophila; D019485:Bone Morphogenetic Proteins; D050659:Core Binding Factor Alpha 1 Subunit; D050660:Core Binding Factors; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D009363:Neoplasm Proteins; C493709:RUNX2 protein, human; D051785:Smad Proteins; D015534:Trans-Activators; D050656:Transcription Factor AP-2; D014157:Transcription Factors; D016212:Transforming Growth Factor beta