Epigenetic Regulation of Adipogenesis

脂肪生成的表观遗传调控

基本信息

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
项目类别：
财政年份：
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

项目摘要

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).

在21世纪，绝大多数组蛋白甲基转移酶和脱甲基酶都是鉴定出来的，但它们的生物学功能知之甚少。我们使用脂肪形成作为模型系统来研究组蛋白甲基转移酶和去甲基酶的作用，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中。我们对组蛋白H3的K4，K9，K27和K36上的甲基化感兴趣（分别为H3K4，H3K9，H3K27和H3K36）。 Polycomb抑制复合物2（PRC2）是动物发育的主要调节剂。 PRC2主要通过其酶促亚基EZH2介导的H3K27（H3K27me3）上的酶促亚基EZH2介导的三甲基化抑制基因表达。使用EZH2有条件的KO前脂肪细胞，我们报告说EZH2及其H3K27甲基转移酶活性是脂肪发生所必需的，并且EZH2构成构成抑制Wnt基因以促进脂肪形成（Wang L，PNAS 2010）。组蛋白甲基转移酶G9A负责H3K9二甲基化（H3K9ME2），这是一种基因抑制的表观遗传标记。使用G9A条件KO前脂肪细胞，我们最近报告说G9A抑制了ppargamma的表达和脂肪形成。 G9A调节脂肪形成的正主调节剂和负基主要调节剂：G9A抑制pPargamma的表达取决于其H3K9甲基转移酶活性，而促进与其酶促活性无关的WNT表达（Wang L，Embo J 2013）。我们最近发现，组蛋白H3赖氨酸（K）的K-TO-M突变强烈抑制脂肪形成。以及我们的报告，包括H3K4ME1/2甲基转移酶MLL3/MLL4是Ppargamma和C/C/EBPALPHA表达和脂肪形成所必需的（Lee Je，Elife，2013年），这些发现提供了对脂肪形成的表观遗传调节的初步观点，并建议对BAINED甲基甲基甲基甲基甲基甲基甲基的表达和负面的甲基甲基甲基甲基甲基甲基甲基化的表达和负态甲基甲基甲基甲基甲基甲基化的表达（ADIP）的表达，ADIP及其甲基甲基甲基甲基甲基甲基甲基甲基甲基甲基的表达及其甲基甲基甲基甲基甲基甲基的表达及其ADIP的表达（ 2014）。组蛋白乙酰转移酶（HAT）GCN5对于胚胎发生至关重要，并显示出其同源性PCAF的部分功能冗余。但是，GCN5和PCAF的组织和细胞谱系特异性功能仍然没有很好地定义。在最近的一项研究中，我们探究了GCN5和PCAF在脂肪形成中的功能。我们发现GCN5/PCAF的双敲除（DKO）抑制了主脂肪生成转录因子基因ppargamma的表达，从而防止了脂肪细胞分化。 GCN5/PCAF DKO细胞中的脂肪形成缺陷是通过PPARGAMMA异位表达挽救的，这表明PPARGAMMA上游的GCN5/PCAF作用以促进脂肪形成。 GCN5/PCAF对PPARGAMMA表达的需求意外地绕过了用脂肪诱导剂3-异丁基-1-甲基黄嘌呤（IBMX）的长时间处理。但是，ppargamma异位表达或延长IBMX治疗均未挽救DKO细胞中PRDM16表达中的缺陷，这表明GCN5/PCAF对于正常的PRDM16表达至关重要。 GCN5/PCAF在转录过程的不同步骤下调节pPargamma和PrdM16表达，促进RNA聚合酶II募集到PRDM16和PPARGAMMA转录本的伸长。总体而言，我们的研究表明，GCN5/PCAF通过调节ppargamma表达来促进脂肪形成，并通过影响PRDM16表达来调节棕色脂肪形成（Jin Q.等，2014）。