Epigenetic Regulation of Adipogenesis

脂肪生成的表观遗传调控

• 批准号: 9148905
• 负责人: Kai Ge
• 金额: $ 45.94万
• 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/9148905
• 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; Mediating; Methylation; Methyltransferase; Morbidity - disease rate; 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; Transcription factor genes; 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). 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).

绝大多数组蛋白甲基转移酶和去甲基化酶是在21世纪发现的，但它们的生物学功能尚不清楚。我们以脂肪形成为模型系统，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中的调节作用。我们对组蛋白H3的K4、K9、K27和K36的甲基化感兴趣（分别是H3K4、H3K9、H3K27和H3K36）。Polycomb suppression complex 2 （PRC2）是动物发育的主要调控因子。PRC2主要通过其酶亚基ezh2介导的H3K27上的三甲基化（H3K27me3）抑制基因表达。利用Ezh2条件KO前脂肪细胞，我们报道了Ezh2及其H3K27甲基转移酶活性是脂肪形成所必需的，并且Ezh2组成性地抑制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），这是基因抑制的表观遗传标记。利用G9a条件KO前脂肪细胞，我们最近报道了G9a抑制PPARgamma表达和脂肪形成。G9a调节脂肪形成的正负主调控因子：G9a通过H3K9甲基转移酶活性抑制PPARgamma的表达，而不依赖于其酶活性促进Wnt的表达（Wang L, EMBO J 2013）。再加上我们关于H3K4me1/2甲基转移酶MLL3/MLL4是PPARgamma和C/EBPalpha表达和脂肪形成所必需的报告（Lee JE, eLife 2013），这些发现提供了脂肪形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形成的阳性和阴性主调控因子的表达（BBA 2012和Cell & Biosci 2014）。