Re-patterning of H3K27me3, H3K4me3 and DNA methylation during fibroblast conversion into induced cardiomyocytes.
Re-patterning of H3K27me3, H3K4me3 and DNA methylation during fibroblast conversion into induced cardiomyocytes.
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DOI：
10.1016/j.scr.2016.02.037
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发表时间：
2016-03
影响因子：
1.2
通讯作者：
Qian L
中科院分区：
文献类型：
--
作者：
Liu Z;Chen O;Zheng M;Wang L;Zhou Y;Yin C;Liu J;Qian L
将成纤维细胞直接转化为诱导心肌细胞（iCM）为心脏病建模和再生提供了另一种策略。在 iCM 重编程过程中，起始成纤维细胞必须克服现有的表观遗传障碍，以获得类似 CM 的染色质模式。然而，这一重编程过程的表观遗传动力学尚未得到研究。在这里，我们利用我们最近生成的多顺反子系统，确定了两个关键组蛋白标记 H3K27me3 和 H3K4me3 的动态，同时在 iCM 重编程期间一组精心选择的心脏和成纤维细胞位点的基因表达。我们早在第 3 天就观察到心脏启动子处 H3K27me3 减少和 H3K4me3 增加，同时其 mRNA 表达迅速显着增加。相比之下，编码成纤维细胞标记基因的位点上的 H3K27me3 直到第 10 天才增加，而 H3K4me3 在重编程过程中逐渐减少；这些变化伴随着成纤维细胞标记基因 mRNA 表达的逐渐下降。对富含成纤维细胞的转录因子的进一步分析显示，H3K27me3 也有类似的晚期沉积，并且 Sox9、Twist1 和 Twist2（上皮-间质转化中的三个重要参与者）的 mRNA 表达降低。我们的数据表明心脏程序的早期快速激活和随后在表观遗传和转录水平上逐渐抑制成纤维细胞的命运。此外，我们确定了代表性心脏启动子的 DNA 甲基化状态，发现并非每个 CpG 在 iCM 重编程的早期阶段都同样去甲基化。相反，存在一些特定的 CpG，其去甲基化状态与转录激活密切相关，我们认为它们是主要的 CpG。因此，我们的工作揭示了 iCM 重编程期间心脏和成纤维细胞位点上 H3K27me3、H3K4me3 的差异重模式，并可为未来的全基因组表观遗传学研究提供重要指导，例如用作阳性和阴性对照的适当时间窗和位点。
Direct conversion of fibroblasts into induced cardiomyocytes (iCMs) offers an alternative strategy for cardiac disease modeling and regeneration. During iCM reprogramming, the starting fibroblasts must overcome existing epigenetic barriers to acquire the CM-like chromatin pattern. However, epigenetic dynamics along this reprogramming process have not been studied. Here, we took advantage of our recently generated polycistronic system and determined the dynamics of two critical histone marks, H3K27me3 and H3K4me3, in parallel with gene expression at a set of carefully selected cardiac and fibroblast loci during iCM reprogramming. We observed reduced H3K27me3 and increased H3K4me3 at cardiac promoters as early as day 3, paralleled by a rapid significant increase in their mRNA expression. In contrast, H3K27me3 at loci encoding fibroblast marker genes did not increase until day 10 and H3K4me3 progressively decreased along the reprogramming process; these changes were accompanied by a gradual decrease in the mRNA expression of fibroblast marker genes. Further analyses of fibroblast-enriched transcription factors revealed a similarly late deposition of H3K27me3 and decreased mRNA expression of Sox9, Twist1 and Twist2, three important players in epithelial-mesenchymal transition. Our data suggest early rapid activation of the cardiac program and later progressive suppression of fibroblast fate at both epigenetic and transcriptional levels. Additionally, we determined the DNA methylation states of representative cardiac promoters and found that not every single CpG was equally demethylated during early stage of iCM reprogramming. Rather, there are specific CpGs, whose demethylation states correlated tightly with transcription activation, that we propose are the major contributing CpGs. Our work thus reveals a differential re-patterning of H3K27me3, H3K4me3 at cardiac and fibroblast loci during iCM reprogramming and could provide future genome-wide epigenetic studies with important guidance such as the appropriate time window and loci to be utilized as positive and negative controls.