Smooth muscle cells and myofibroblasts use distinct transcriptional mechanisms for smooth muscle α-actin expression
Smooth muscle cells and myofibroblasts use distinct transcriptional mechanisms for smooth muscle α-actin expression
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DOI：
10.1161/circresaha.107.154831
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发表时间：
2007-10-26
影响因子：
20.1
通讯作者：
Owens, Gary K.
中科院分区：
文献类型：
--
作者：
Gan, Qiong;Yoshida, Tadashi;Owens, Gary K.
关于平滑肌细胞（SMC）和肌成纤维细胞之间的谱系关系存在相当大的争议，因为它们表达许多常见的细胞选择性标记物，包括平滑肌（SM）α-肌动蛋白。我们以前已经表明，SM α-肌动蛋白启动子内的MCAT元件赋予培养的SMC与肌成纤维细胞的差异活性。在本研究中，为了确定MCAT元件在体内的作用，我们产生了一个SM α-肌动蛋白启动子-增强子-LacZ报告基因含有MCAT元件突变的转基因小鼠，并与野生型SM α-肌动蛋白启动子-增强子-LacZ转基因小鼠的转基因表达模式进行了比较。结果表明，LacZ的表达模式在成人SMC的组织中没有差异。然而，令人感兴趣的是，MCAT元件的突变选择性地消除了皮肤伤口肉芽组织内肌成纤维细胞中的转基因表达。此外，MCAT元件的突变导致SMC中转基因表达的诱导延迟，以及胚胎发生期间心肌和骨骼肌中表达的丧失。小干扰RNA诱导的敲低实验结果表明，RTEF-1调节肌成纤维细胞中SM α-肌动蛋白的转录，但不调节分化的SMC中的SM α-肌动蛋白的转录。此外，定量染色质免疫沉淀分析显示，RTEF-1结合到MCAT元件内的SM α-肌动蛋白启动子在肌成纤维细胞的区域，而转录增强因子（TEF）-1结合到同一地区在分化的SMC。这些结果提供了新的证据，表明尽管SMC和肌成纤维细胞都表达SM α-肌动蛋白，但它们使用不同的转录控制机制来调节其表达。结果还表明，MCAT元件突变的SM α-肌动蛋白启动子-增强子是在分化的SMC中选择性指导基因表达的有用工具。
There has been considerable controversy regarding the lineage relationship between smooth muscle cells (SMCs) and myofibroblasts, because they express a number of common cell-selective markers including smooth muscle (SM) alpha-actin. We have shown previously that MCAT elements within the SM alpha-actin promoter confer differential activity in cultured SMCs versus myofibroblasts. In the present study, to determine the role of MCAT elements in vivo, we generated transgenic mice harboring an SM alpha-actin promoter-enhancer-LacZ reporter gene containing MCAT element mutations and compared transgene expression patterns with wild-type SM alpha-actin promoter-enhancer-LacZ transgenic mice. Results showed no differences in LacZ expression patterns in adult SMC-containing tissues. However, of interest, mutations of MCAT elements selectively abolished transgene expression in myofibroblasts within granulation tissue of skin wounds. In addition, mutations of MCAT elements caused a delay in the induction of transgene expression in SMCs, as well as loss of expression in cardiac and skeletal muscles during embryogenesis. Results of small interfering RNA-induced knockdown experiments showed that RTEF-1 regulated SM alpha-actin transcription in myofibroblasts, but not in differentiated SMCs. Moreover, quantitative chromatin immunoprecipitation assays revealed that RTEF-1 bound to the MCAT element-containing region within the SM alpha-actin promoter in myofibroblasts, whereas transcriptional enhancer factor (TEF)-1 was bound to the same region in differentiated SMCs. These results provide novel evidence that, although both SMCs and myofibroblasts express SM alpha-actin, they use distinct transcriptional control mechanisms for regulating its expression. Results also indicate that the MCAT element-mutated SM alpha-actin promoter-enhancer is a useful tool to direct gene expression selectively in differentiated SMCs.