Bae S C, Lee K S, Zhang Y W, Ito Y
Department of Biochemistry, School of Medicine, and Medical Research Institute, Chungbuk National University, Cheongju, Korea.
J Bone Joint Surg Am. 2001;83-A Suppl 1(Pt 1):S48-55.
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.
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.
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.
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.
当用转化生长因子-β1（TGF-β1）处理C2C12多能间充质前体细胞时，其向肌管的终末分化被阻断。用骨形态发生蛋白-2（BMP-2）处理不仅会阻断肌源性分化，还会诱导成骨细胞分化。然而，调控TGF-β和BMP诱导配体特异性反应及抑制肌源性分化能力的分子机制尚不清楚。我们研究的目的是阐明在C2C12细胞中阻断成肌细胞分化并诱导成骨细胞分化的分子机制。
通过电泳迁移率变动分析（EMSA）和Northern印迹分析检测TGF-β和BMP对RUNX2/PEBP2αA/Cbfa1的诱导作用。建立稳定表达RUNX2或Smad或两者的C2C12细胞系，并通过检测成骨细胞特异性标志物的表达来分析这些基因在成骨细胞分化过程中的作用。
用TGF-β和BMP处理C2C12可诱导RUNX2/PEBP2αA/Cbfa1，这是一种成骨作用的全局调节因子。RUNX2与BMP激活的Smad之间的协同作用诱导了成骨细胞分化。
TGF-β和BMP均可激活RUNX2的转录，这足以抑制肌生成。为诱导成骨，BMP诱导的RUNX2必须与BMP激活的Smad协同作用。
