Fibroblast growth factor 10 gene regulation in the second heart field by Tbx1, Nkx2-5, and Islet1 reveals a genetic switch for down-regulation in the myocardium
Fibroblast growth factor 10 gene regulation in the second heart field by Tbx1, Nkx2-5, and Islet1 reveals a genetic switch for down-regulation in the myocardium
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DOI：
10.1073/pnas.1215360109
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发表时间：
2012-10
期刊：
影响因子：
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通讯作者：
Yusuke Watanabe;S. Zaffran;A. Kuroiwa;Hiroaki Higuchi;T. Ogura;R. Harvey;R. Kelly;M. Buckingham
中科院分区：
文献类型：
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作者：
Yusuke Watanabe;S. Zaffran;A. Kuroiwa;Hiroaki Higuchi;T. Ogura;R. Harvey;R. Kelly;M. Buckingham
在心脏发生过程中，成纤维细胞生长因子（Fgf10）在第二心前区表达。与成纤维细胞生长因子8 （Fgf8）一起，Fgf10促进这些形成心脏动脉极的心脏祖细胞的增殖。我们已经在Fgf10的第一个内含子中发现了一个1.7 kb的区域，该区域是在这种心脏环境下指导转基因表达所必需和充分的。这个1.7 kb的序列是由第二心前区细胞中的T-box转录因子1 （Tbx1）直接控制的。它还响应NK2转录因子相关的位点5 （Nkx2-5）和ISL1转录因子LIM/同源结构域（Islet1），通过重叠位点起作用。这些位点的突变减少了第二心脏前区Fgf10调控元件在体内通过直接结合被Islet1激活的转基因表达。对Nkx2-5缺失和Isl1功能获得遗传背景的反应分析表明，在Nkx2-5突变体心脏中观察到的其活性上调，反映了Fgf10，这是由于Nkx2-5不受抑制，而在心肌中通常被Nkx2-5抑制的Isl1上调。ChIP实验显示Nkx2-5在分化心肌中有较强的结合。因此，对Fgf10心脏元件的分子和遗传分析揭示了关键的心脏转录因子如何协调第二心脏前区基因表达，以及Fgf10等通常在祖细胞群中表达的基因如何在这些细胞进入心脏并分化成心肌时受到抑制。我们的研究结果为从祖细胞状态到分化组织状态转变过程中调控网络变化的转录机制提供了一个范例。
During cardiogenesis, Fibroblast Growth Factor (Fgf10) is expressed in the anterior second heart field. Together with Fibroblast growth factor 8 (Fgf8), Fgf10 promotes the proliferation of these cardiac progenitor cells that form the arterial pole of the heart. We have identified a 1.7-kb region in the first intron of Fgf10 that is necessary and sufficient to direct transgene expression in this cardiac context. The 1.7-kb sequence is directly controlled by T-box transcription factor 1 (Tbx1) in anterior second heart field cells that contribute to the outflow tract. It also responds to both NK2 transcription factor related, locus 5 (Nkx2-5) and ISL1 transcription factor, LIM/homeodomain (Islet1), acting through overlapping sites. Mutation of these sites reduces transgene expression in the anterior second heart field where the Fgf10 regulatory element is activated by Islet1 via direct binding in vivo. Analysis of the response to Nkx2-5 loss- and Isl1 gain-of-function genetic backgrounds indicates that the observed up-regulation of its activity in Nkx2-5 mutant hearts, reflecting that of Fgf10, is due to the absence of Nkx2-5 repression and to up-regulation of Isl1, normally repressed in the myocardium by Nkx2-5. ChIP experiments show strong binding of Nkx2-5 in differentiated myocardium. Molecular and genetic analysis of the Fgf10 cardiac element therefore reveals how key cardiac transcription factors orchestrate gene expression in the anterior second heart field and how genes, such as Fgf10, normally expressed in the progenitor cell population, are repressed when these cells enter the heart and differentiate into myocardium. Our findings provide a paradigm for transcriptional mechanisms that underlie the changes in regulatory networks during the transition from progenitor state to that of the differentiated tissue.