BMP2 commitment to the osteogenic lineage involves activation of Runx2 by DLX3 and a homeodomain transcriptional network
BMP2 commitment to the osteogenic lineage involves activation of Runx2 by DLX3 and a homeodomain transcriptional network
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DOI：
10.1074/jbc.m604508200
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发表时间：
2006-12-29
影响因子：
4.8
通讯作者：
Lian, Jane B.
中科院分区：
文献类型：
--
作者：
Hassan, Mohammad Q.;Tare, Rahul S.;Lian, Jane B.
几种同源结构域 (HD) 蛋白对于骨骼模式至关重要，并直接响应 BMP2 作为骨形成的早期步骤。 RUNX2 是最早被证明对成骨细胞生成至关重要的转录因子，它也响应 BMP2 而表达。然而，我们对从 BMP2 信号传导到成骨开始的调控级联的了解存在差距。在这里，我们表明 BMP2 诱导 DLX3，这是一种激活 Runx2 基因转录的同源域蛋白。成骨细胞中的小干扰 RNA 敲除研究证实 DLX3 是 Runx2 的有效调节因子。此外，在Runx2无效细胞中，DLX3强制表达足以诱导Runx2、骨钙素和碱性磷酸酶基因的转录，从而将DLX3定义为独立于RUNX2的成骨调节剂。我们的研究进一步表明 Runx2 基因受到几种同源域蛋白的调节：MSX2 和 CDP/cut 抑制，而 DLX3 和 DLX5 激活非骨细胞和成骨细胞中的内源 Runx2 表达和启动子活性。这些 HD 蛋白在成骨细胞分化过程中表现出独特的时间表达谱，并与 Runx2 染色质选择性关联，这与 Runx2 转录活性和 RNA 聚合酶 II 的募集有关。 Runx2 启动子诱变表明，多个 HD 元件控制与成骨细胞成熟阶段相关的 Runx2 表达。我们的研究建立了通过 BMP2 诱导 HD 蛋白 DLX3 和 DLX5（激活 Runx2）直接形成成骨谱系的机制，从而描绘了介导成骨细胞分化的转录调控途径。我们提出三种同源域蛋白 MSX2、DLX3 和 DLX5 提供了一系列关键的分子开关，在整个骨形成过程中调节 Runx2 的表达。
Several homeodomain (HD) proteins are critical for skeletal patterning and respond directly to BMP2 as an early step in bone formation. RUNX2, the earliest transcription factor proven essential for commitment to osteoblastogenesis, is also expressed in response to BMP2. However, there is a gap in our knowledge of the regulatory cascade from BMP2 signaling to the onset of osteogenesis. Here we show that BMP2 induces DLX3, a homeodomain protein that activates Runx2 gene transcription. Small interfering RNA knockdown studies in osteoblasts validate that DLX3 is a potent regulator of Runx2. Furthermore in Runx2 null cells, DLX3 forced expression suffices to induce transcription of Runx2, osteocalcin, and alkaline phosphatase genes, thus defining DLX3 as an osteogenic regulator independent of RUNX2. Our studies further show regulation of the Runx2 gene by several homeodomain proteins: MSX2 and CDP/cut repress whereas DLX3 and DLX5 activate endogenous Runx2 expression and promoter activity in non-osseous cells and osteoblasts. These HD proteins exhibit distinct temporal expression profiles during osteoblast differentiation as well as selective association with Runx2 chromatin that is related to Runx2 transcriptional activity and recruitment of RNA polymerase II. Runx2 promoter mutagenesis shows that multiple HD elements control expression of Runx2 in relation to the stages of osteoblast maturation. Our studies establish mechanisms for commitment to the osteogenic lineage directly through BMP2 induction of HD proteins DLX3 and DLX5 that activate Runx2, thus delineating a transcriptional regulatory pathway mediating osteoblast differentiation. We propose that the three homeodomain proteins MSX2, DLX3, and DLX5 provide a key series of molecular switches that regulate expression of Runx2 throughout bone formation.