Epigenetic Regulation of Adipogenesis

脂肪生成的表观遗传调控

• 批准号: 9356191
• 负责人: Kai Ge
• 金额: $ 47.73万
• 依托单位: NATIONAL INSTITUTE OF DIABETES AND DIGESTIVE AND KIDNEY DISEASES
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/9356191
• 关键词: Accounting; Acetylation; Animals; Biological Models; Biological Process; Bypass; CCAAT-Enhancer-Binding Protein-alpha; Cell Differentiation process; Cell Lineage; Cells; Complex; Defect; Development; Diabetes Mellitus; Ectopic Expression; Embryonic Development; Epigenetic Process; Fatty acid glycerol esters; G9a histone methyltransferase; Gene Expression; Gene Expression Regulation; Generations; Genes; Histone H3; Histones; Homologous Gene; Knock-out; Lysine; Mediating; Methylation; Methyltransferase; Morbidity - disease rate; Mutation; Non-Insulin-Dependent Diabetes Mellitus; Obesity; PCAF gene; PPAR gamma; Play; Polycomb; RNA Polymerase II; Regulation; Reporting; Risk Factors; Role; Signal Transduction; Site; Tissues; Transcript; Transcription Process; adipocyte differentiation; beta catenin; epigenetic regulation; gene repression; histone acetyltransferase; histone demethylase; histone methylation; histone methyltransferase; histone modification; interest; lipid biosynthesis; methylxanthine; mortality; prevent; transcription factor

The vast majority of histone methyltransferases and demethylases were identified in the 21st century but their biological functions are poorly understood. We use adipogenesis as a model system to study the roles of histone methyltransferases and demethylases, and the dynamics of site-specific histone methylation, in regulation of gene expression and cell differentiation. We are interested in methylations on K4, K9, K27 and K36 of histone H3 (H3K4, H3K9, H3K27 and H3K36, respectively). The Polycomb repressive complex 2 (PRC2) is a major regulator of animal development. PRC2 represses gene expression mainly through its enzymatic subunit Ezh2-mediated tri-methylation on H3K27 (H3K27me3). Using Ezh2 conditional KO preadipocytes, we report that Ezh2 and its H3K27 methyltransferase activity are required for adipogenesis and that Ezh2 constitutively represses Wnt genes to facilitate adipogenesis (Wang L, PNAS 2010). Histone methyltransferase G9a is responsible for H3K9 di-methylation (H3K9me2), an epigenetic mark for gene repression. Using G9a conditional KO preadipocytes, we report recently that G9a represses PPARgamma expression and adipogenesis. G9a regulates both positive and negative master regulators of adipogenesis: G9a represses PPARgamma expression dependent on its H3K9 methyltransferase activity while promotes Wnt expression independent of its enzymatic activity (Wang L, EMBO J 2013). We have recently found that K-to-M mutation of histone H3 lysine (K) 36 strongly inhibits adipogenesis. Together with our reports that H3K4me1/2 methyltransferases MLL3/MLL4 are required for PPARgamma and C/EBPalpha expression and adipogenesis (Lee JE, eLife 2013), these findings provide an initial view of epigenetic regulation of adipogenesis, and suggest that histone methylations control expression of positive and negative master regulators of adipogenesis (reviewed in BBA 2012 and Cell & Biosci 2014). Histone acetyltransferase (HAT) Gcn5 is critical for embryogenesis and shows partial functional redundancy with its homolog PCAF. However, the tissue- and cell lineage-specific functions of Gcn5 and PCAF are still not well defined. In a recent study, we probe the functions of Gcn5 and PCAF in adipogenesis. We found that the double knockout (DKO) of Gcn5/PCAF inhibits expression of the master adipogenic transcription factor gene PPARgamma, thereby preventing adipocyte differentiation. The adipogenesis defects in Gcn5/PCAF DKO cells are rescued by ectopic expression of PPARgamma, suggesting Gcn5/PCAF act upstream of PPARgamma to facilitate adipogenesis. The requirement of Gcn5/PCAF for PPARgamma expression was unexpectedly bypassed by prolonged treatment with an adipogenic inducer, 3-isobutyl-1-methylxanthine (IBMX). However, neither PPARgamma ectopic expression nor prolonged IBMX treatment rescued defects in Prdm16 expression in DKO cells, indicating that Gcn5/PCAF are essential for normal Prdm16 expression. Gcn5/PCAF regulate PPARgamma and Prdm16 expression at different steps in the transcription process, facilitating RNA polymerase II recruitment to Prdm16 and elongation of PPARgamma transcripts. Overall, our study reveals that Gcn5/PCAF facilitate adipogenesis through regulation of PPARgamma expression and regulate brown adipogenesis by influencing Prdm16 expression (Jin Q. et al., 2014).

大多数组蛋白甲基转移酶和去甲基化酶是在21世纪世纪发现的，但其生物学功能尚不清楚。我们使用脂肪形成作为一个模型系统来研究组蛋白甲基转移酶和去甲基化酶的作用，以及位点特异性组蛋白甲基化的动力学，在基因表达和细胞分化的调节。我们感兴趣的是组蛋白H3的K4、K9、K27和K36（分别为H3 K4、H3 K9、H3 K27和H3 K36）上的甲基化。 Polycomb repressive complex 2（PRC 2）是动物发育的主要调节因子。PRC 2主要通过其酶亚基Ezh 2介导的H3 K27（H3 K27 me 3）上的三甲基化来抑制基因表达。使用Ezh 2条件性KO前脂肪细胞，我们报告了Ezh 2及其H3 K27甲基转移酶活性是脂肪生成所需的，并且Ezh 2组成型抑制Wnt基因以促进脂肪生成（Wang L，PNAS 2010）。组蛋白甲基转移酶G9 a负责H3 K9二甲基化（H3 K9 me 2），这是基因阻遏的表观遗传标记。使用G9 a条件KO前脂肪细胞，我们最近报道G9 a抑制PPARgamma表达和脂肪生成。G9 a调节脂肪形成的正性和负性主调节因子：G9 a依赖于其H3 K9甲基转移酶活性抑制PPARgamma表达，同时独立于其酶活性促进Wnt表达（Wang L，EMBO J 2013）。我们最近发现组蛋白H3赖氨酸（K）36的K-至-M突变强烈抑制脂肪生成。结合我们的报告，即H3 K4 me 1/2甲基转移酶MLL 3/MLL 4是PPARgamma和C/EBPalpha表达和脂肪生成所必需的（Lee JE，eLife 2013），这些发现提供了脂肪生成的表观遗传调控的初步观点，并表明组蛋白甲基化控制脂肪生成的阳性和阴性主调节因子的表达（在BBA 2012和Cell & Biosci 2014中综述）。 组蛋白乙酰转移酶（HAT）Gcn 5是胚胎发生的关键，并显示部分功能冗余与其同源物PCAF。然而，Gcn 5和PCAF的组织和细胞系特异性功能仍然没有很好地定义。在最近的一项研究中，我们探讨了Gcn 5和PCAF在脂肪形成中的功能。我们发现Gcn 5/PCAF的双敲除（DKO）抑制了主成脂转录因子基因PPARgamma的表达，从而阻止了脂肪细胞分化。Gcn 5/PCAF DKO细胞中的脂肪生成缺陷被PPARgamma的异位表达所挽救，表明Gcn 5/PCAF在PPARgamma的上游起作用以促进脂肪生成。通过用脂肪形成诱导剂3-异丁基-1-甲基黄嘌呤（IBMX）长时间处理，出乎意料地绕过了Gcn 5/PCAF对PPARgamma表达的要求。然而，无论是PPARgamma异位表达还是延长IBMX处理都不能挽救DKO细胞中Prdm 16表达的缺陷，表明Gcn 5/PCAF对于正常Prdm 16表达是必需的。Gcn 5/PCAF在转录过程的不同步骤调节PPARgamma和Prdm 16的表达，促进RNA聚合酶II募集到Prdm 16和PPARgamma转录物的延伸。总的来说，我们的研究揭示了Gcn 5/PCAF通过调节PPARgamma表达促进脂肪形成，并通过影响Prdm 16表达调节棕色脂肪形成（Jin Q.例如，2014年）。