BMP2 Regulates Osterix through Msx2 and Runx2 during Osteoblast Differentiation
BMP2 Regulates Osterix through Msx2 and Runx2 during Osteoblast Differentiation
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DOI：
10.1074/jbc.m801774200
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发表时间：
2008-10-24
影响因子：
4.8
通讯作者：
Yoneda, Toshiyuki
中科院分区：
文献类型：
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作者：
Matsubara, Takuma;Kida, Kumiko;Yoneda, Toshiyuki
Osterix/SP7是Sp1转录因子家族的成员，在骨形成和成骨细胞形成中起重要作用。虽然已经证明Osterix是由BMP2在间充质细胞系中诱导的，但Osterix在成骨细胞分化过程中的调控、表达和功能的分子基础还不完全清楚。因此，我们利用间充质细胞系C3H10T1/2和C2C12研究了BMP2信号在Osterix调控中的作用。Osterix过表达诱导C2C12细胞碱性磷酸酶活性和骨钙素表达，并刺激小鼠原代成骨细胞钙化。考虑到Runx2的过表达诱导了Osterix，这些结果表明Osterix作为Runx2的下游发挥作用。令人惊讶的是，BMP2处理诱导了Runx2缺陷小鼠来源的间充质细胞中Osterix的表达和碱性磷酸酶的活性。此外，Smad1和Smad4的过表达上调了Osterix的表达，而抑制Smad6的Smad6显著抑制了BMP2诱导的Runx2缺陷细胞中Osterix的表达。此外，由BMP2上调并促进成骨细胞分化的同源盒基因MSX2的过度表达，诱导了Runx2缺陷细胞中Osterix的表达。MSX2基因敲除可明显抑制BMP2对Runx2缺陷间充质细胞诱导Osterix的作用。有趣的是，使用Runx2缺陷细胞的微阵列分析显示，Osterix的作用与Runx2不同。这些发现表明，Osterix通过Runx2依赖和非依赖的机制来调节，并且Osterix至少部分地通过调节不受Runx2控制的基因的表达来控制成骨细胞的分化。
Osterix/Sp7, a member of the Sp1 transcription factor family, plays an essential role in bone formation and osteoblastogenesis. Although Osterix has been shown to be induced by BMP2 in a mesenchymal cell line, the molecular basis of the regulation, expression and function of Osterix during osteoblast differentiation, is not fully understood. Thus we examined the role of BMP2 signaling in the regulation of Osterix using the mesenchymal cell lines C3H10T1/2 and C2C12. Osterix overexpression induced alkaline phosphatase activity and osteocalcin expression in C2C12 cells and stimulated calcification of murine primary osteoblasts. Considering that Runx2 overexpression induces Osterix, these results suggest that Osterix functions as downstream of Runx2. Surprisingly, BMP2 treatment induced Osterix expression and alkaline phosphatase activity in mesenchymal cells derived from Runx2-deficient mice. Furthermore, overexpression of Smad1 and Smad4 up-regulated Osterix expression, and an inhibitory Smad, Smad6, markedly suppressed BMP2-induced Osterix expression in the Runx2-deficient cells. Moreover, overexpression of a homeobox gene, Msx2, which is up-regulated by BMP2 and promotes osteoblastic differentiation, induced Osterix expression in the Runx2-deficient cells. Knockdown of Msx2 clearly inhibited induction of Osterix by BMP2 in the Runx2-deficient mesenchymal cells. Interestingly, microarray analyses using the Runx2-deficient cells revealed that the role of Osterix was distinct from that of Runx2. These findings suggest that Osterix is regulated via both Runx2-dependent and -independent mechanisms, and that Osterix controls osteoblast differentiation, at least in part, by regulating the expression of genes not controlled by Runx2.