Lee Y-J, Park S-Y, Lee S-J, Boo Y C, Choi J-Y, Kim J-E
Cell and Matrix Research Institute, Department of Molecular Medicine, Kyungpook National University School of Medicine, Daegu, Republic of Korea; BK21 Plus KNU Biomedical Convergence Program, Department of Biomedical Science, Kyungpook National University, Daegu, Republic of Korea.
Department of Biochemistry, School of Medicine, Dongguk University, Gyeongju, Republic of Korea.
Osteoarthritis Cartilage. 2015 Aug;23(8):1421-31. doi: 10.1016/j.joca.2015.03.035. Epub 2015 Apr 9.
Runt-related transcription factor 2 (Runx2) and Osterix (Osx) are the master transcription factors in bone formation. Nonetheless, genes acting downstream of both Runx2 and Osx have yet to be fully characterized. Here, we investigate the downstream targets of both Runx2 and Osx in osteoblasts.
DNA microarray analysis was conducted on calvarial RNA from wild-type, Runx2 heterozygous, Osx heterozygous, and Runx2/Osx double heterozygous embryos. Expression and transcriptional responses of the selected target gene were analyzed in MC3T3-E1 osteoblastic cells.
The expression of unique cartilage matrix-associated protein (Ucma) was decreased in Runx2/Osx double heterozygous embryos. In contrast, Ucma expression was increased in osteoblasts overexpressing both Runx2 and Osx. Ucma expression was initiated mid-way through osteoblast differentiation and continued throughout the differentiation process. Transcriptional activity of the Ucma promoter was increased upon transfection of the cells with both Runx2 and Osx. Runx2-and Osx-mediated activation of the Ucma promoter was directly regulated by Runx2-and/or Sp1-binding sites within its promoter. During osteoblast differentiation, the formation of mineralized nodules in Ucma-overexpressing stable clones occurred earlier and was more enhanced than that in the mock-transfected control. Mineralized nodule formation was strongly augmented in the cells cultured in a medium containing secretory Ucma proteins.
Ucma is a novel downstream gene regulated by both Runx2 and Osx and it stimulates osteoblast differentiation and nodule formation.
runt相关转录因子2（Runx2）和osterix（Osx）是骨形成过程中的主要转录因子。然而，Runx2和Osx下游的作用基因尚未完全明确。在此，我们研究了成骨细胞中Runx2和Osx的下游靶点。
对野生型、Runx2杂合子、Osx杂合子以及Runx2/Osx双杂合子胚胎的颅骨RNA进行DNA微阵列分析。在MC3T3-E1成骨细胞中分析所选靶基因的表达和转录反应。
在Runx2/Osx双杂合子胚胎中，独特软骨基质相关蛋白（Ucma）的表达降低。相反，在同时过表达Runx2和Osx的成骨细胞中，Ucma表达增加。Ucma表达在成骨细胞分化中期开始，并在整个分化过程中持续。用Runx2和Osx转染细胞后，Ucma启动子的转录活性增加。Runx2和Osx介导的Ucma启动子激活直接受其启动子内Runx2和/或Sp1结合位点的调控。在成骨细胞分化过程中，Ucma过表达稳定克隆中矿化结节的形成比mock转染对照更早且更明显。在含有分泌型Ucma蛋白的培养基中培养的细胞中，矿化结节形成显著增强。
Ucma是受Runx2和Osx共同调控的一个新的下游基因，它刺激成骨细胞分化和结节形成。
