Twisted gastrulation modulates bone morphogenetic protein-induced collagen II and X expression in chondrocytes in vitro and in vivo
Twisted gastrulation modulates bone morphogenetic protein-induced collagen II and X expression in chondrocytes in vitro and in vivo
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DOI：
10.1074/jbc.m603419200
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发表时间：
2006-10-20
影响因子：
4.8
通讯作者：
von der Mark, Klaus
中科院分区：
文献类型：
--
作者：
Schmidl, Martina;Adam, Nadia;von der Mark, Klaus
扭曲原肠胚形成（TSG）是骨形态发生蛋白（BMP）活性的细胞外调节剂，在果蝇和爪蟾的早期发育中调节背腹轴的形成。对TSG缺陷小鼠的研究也表明该蛋白在骨骼生长中起作用，但TSG活性在这一过程中的机制尚未被研究。本研究首次通过原位杂交和免疫组化发现，TSG在牛和小鼠生长板软骨以及胎儿肋骨、椎软骨和颅骨软骨原中均有强烈表达。此外，我们提供的证据表明，TSG直接参与bmp调节的软骨细胞分化和成熟。在体外，TSG损害了MC615软骨细胞和小鼠原代软骨细胞培养中胶原II和X表达的剂量依赖性BMP-2刺激。在BMP拮抗剂chordin的存在下，TSG的抑制作用进一步增强。TSG还能抑制bmp2刺激的软骨细胞中Smad因子的磷酸化，证实TSG作为BMP信号的调节剂的作用。为了分析TSG在体内软骨发育中的功能，在软骨特异性Col2a1启动子的控制下，该基因在转基因小鼠中过表达。结果，原位杂交和实时PCR分析显示，与野生型窝仔相比，转基因胚胎和新生儿的生长板中Col10a1的表达明显降低。这些数据表明，TSG是bmp调节的软骨发育和软骨细胞分化的重要调节剂。
Twisted gastrulation (TSG) is an extracellular modulator of bone morphogenetic protein (BMP) activity and regulates dorsoventral axis formation in early Drosophila and Xenopus development. Studies on tsg-deficient mice also indicated a role of this protein in skeletal growth, but the mechanism of TSG activity in this process has not yet been investigated. Here we show for the first time by in situ hybridization and immunohistochemistry that TSG is strongly expressed in bovine and mouse growth plate cartilage as well as in fetal ribs, vertebral cartilage, and cartilage anlagen of the skull. Furthermore we provide evidence that TSG is directly involved in BMP-regulated chondrocyte differentiation and maturation. In vitro, TSG impaired the dose-dependent BMP-2 stimulation of collagen II and X expression in cultures of MC615 chondrocytes and primary mouse chondrocytes. In the presence of chordin, a BMP antagonist, the inhibitory effect of TSG was further enhanced. TSG also inhibited BMP2-stimulated phosphorylation of Smad factors in chondrocytes, confirming the role of TSG as a modulator of BMP signaling. For analysis of TSG functions in cartilage development in vivo, the gene was overexpressed in transgenic mice under the control of the cartilage-specific Col2a1 promoter. As a result, Col10a1 expression was significantly reduced in the growth plates of transgenic embryos and newborns in comparison with wild type littermates as shown by in situ hybridization and by real time PCR analysis. The data suggest that TSG is an important modulator of BMP-regulated cartilage development and chondrocyte differentiation.