Zheng Qiping, Zhou Guang, Morello Roy, Chen Yuqing, Garcia-Rojas Xavier, Lee Brendan
Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA.
J Cell Biol. 2003 Sep 1;162(5):833-42. doi: 10.1083/jcb.200211089.
The alpha1(X) collagen gene (Col10a1) is the only known hypertrophic chondrocyte-specific molecular marker. Until recently, few transcriptional factors specifying its tissue-specific expression have been identified. We show here that a 4-kb murine Col10a1 promoter can drive beta-galactosidase expression in lower hypertrophic chondrocytes in transgenic mice. Comparative genomic analysis revealed multiple Runx2 (Runt domain transcription factor) binding sites within the proximal human, mouse, and chick Col10a1 promoters. In vitro transfection studies and chromatin immunoprecipitation analysis using hypertrophic MCT cells showed that Runx2 contributes to the transactivation of this promoter via its conserved Runx2 binding sites. When the 4-kb Col10a1 promoter transgene was bred onto a Runx2(+/-) background, the reporter was expressed at lower levels. Moreover, decreased Col10a1 expression and altered chondrocyte hypertrophy was also observed in Runx2 heterozygote mice, whereas Col10a1 was barely detectable in Runx2-null mice. Together, these data suggest that Col10a1 is a direct transcriptional target of Runx2 during chondrogenesis.
α1(X)胶原蛋白基因（Col10a1）是目前已知的唯一一种肥大软骨细胞特异性分子标志物。直到最近，才鉴定出少数几个决定其组织特异性表达的转录因子。我们在此表明，一个4kb的小鼠Col10a1启动子能够驱动转基因小鼠中下层肥大软骨细胞的β-半乳糖苷酶表达。比较基因组分析揭示了在人、小鼠和鸡的Col10a1近端启动子内存在多个Runx2（Runt结构域转录因子）结合位点。使用肥大的MCT细胞进行的体外转染研究和染色质免疫沉淀分析表明，Runx2通过其保守的Runx2结合位点促进该启动子的反式激活。当将4kb的Col10a1启动子转基因培育到Runx2(+/-)背景上时，报告基因的表达水平较低。此外，在Runx2杂合子小鼠中也观察到Col10a1表达降低和软骨细胞肥大改变，而在Runx2基因敲除小鼠中几乎检测不到Col10a1。总之，这些数据表明Col10a1是软骨形成过程中Runx2的直接转录靶点。
