Department of Pathology, University of Michigan Medical School, 109 Zina Pitcher Place, Ann Arbor, MI 48109-2200, USA.
Am J Pathol. 2010 Jul;177(1):21-8. doi: 10.2353/ajpath.2010.090999. Epub 2010 May 20.
DNA methylation, a key mechanism of repressing gene expression, is of particular relevance in controlling development and cell differentiation. We analyzed the extent and regulation of DNA methylation of the alpha-smooth muscle actin (alpha-SMA) gene to elucidate its potential role in myofibroblast differentiation. These experiments revealed the presence of three CpG islands that were methylated at different levels in fibroblasts, myofibroblasts, and alveolar epithelial type II cells. Coordinately, these cells expressed low, high, or no alpha-SMA, respectively. In addition, inhibition of DNA methyltransferase activity or knock down of DNA methyltransferase using specific small interfering RNA caused significant induction of alpha-SMA in fibroblasts. In contrast, induced overexpression of DNA methyltransferase suppressed alpha-SMA gene expression. Transforming growth factor beta induced myofibroblast differentiation was enhanced or suppressed by knockdown or overexpression of DNA methyltransferase, respectively. Finally, in vitro DNA methylation of the alpha-SMA promoter suppressed its activity. These findings suggest that DNA methylation mediated by DNA methyltransferase is an important mechanism regulating the alpha-SMA gene expression during myofibroblast differentiation.
DNA 甲基化是抑制基因表达的关键机制，在控制发育和细胞分化方面具有特别重要的意义。我们分析了α-平滑肌肌动蛋白 (α-SMA) 基因的 DNA 甲基化程度和调控，以阐明其在肌成纤维细胞分化中的潜在作用。这些实验揭示了三个 CpG 岛的存在，这些 CpG 岛在成纤维细胞、肌成纤维细胞和肺泡上皮 II 型细胞中甲基化程度不同。协调地，这些细胞分别表达低、高或无 α-SMA。此外，抑制 DNA 甲基转移酶活性或使用特异性小干扰 RNA 敲低 DNA 甲基转移酶可导致成纤维细胞中 α-SMA 的显著诱导。相比之下，诱导的 DNA 甲基转移酶过表达抑制了 α-SMA 基因的表达。转化生长因子 β诱导的肌成纤维细胞分化分别通过 DNA 甲基转移酶的敲低或过表达增强或抑制。最后，体外 α-SMA 启动子的 DNA 甲基化抑制了其活性。这些发现表明，由 DNA 甲基转移酶介导的 DNA 甲基化是调节肌成纤维细胞分化过程中 α-SMA 基因表达的重要机制。
