Epigenomic Regulation of PPARgamma and Adipogenesis

我们对组蛋白H3的K4、K9、K27、K36和K79（分别为H3 K4、H3 K9、H3 K27、H3 K36和H3 K79）上的位点特异性甲基化在调节脂肪形成和PPARgamma中的作用感兴趣。我们以前报道过，增强子H3 K4 me 1甲基转移酶MLL 3/MLL 4和相关的PTIP控制PPARgamma和C/EBPa的诱导，并且对于脂肪形成是必需的（Cho YW，Cell Metab 2009; Lee JE，eLife 2013; Jang Y，NAR 2019），H3 K9甲基转移酶G9 a抑制PPARgamma表达和脂肪生成（Wang L，EMBO J 2013），H3 K27甲基转移酶Ezh 2组成型抑制Wnt基因以促进脂肪形成（Wang L，PNAS 2010），并且在祖细胞中通过组蛋白H3.3突变体H3.3K36M消耗Nsd 2介导的H3 K36甲基化损害脂肪组织发育和功能（Zhuang L，Nat Comm 2018）。我们还表明，表观基因组阅读器Brd 4控制细胞身份基因诱导，并且对于体内脂肪形成至关重要（Lee JE，Nat Comm 2017）。总之，这些研究结果表明，表观基因组因子在脂肪形成的调控中起着关键作用（Lee JE，MCB 2019中综述）。 使用条件性基因敲除小鼠和前脂肪细胞，我们惊讶地发现，尽管配体结合的糖皮质激素受体（GR）加速了培养物中的脂肪生成，但内源性GR在培养物和小鼠中对脂肪生成不利（Park Y，MCB 2017 a）。 我们还发现，KLF 4和Krox 20在培养物和小鼠中对脂肪形成有抑制作用（Park Y，MCB 2017 b）。这些意想不到的结果促使我们研究体内脂肪形成。 我们先前分析了增强子表观基因组写入器（MLL 4，CBP）、脂肪形成TF（EBF 2，C/EBPa，C/EBPb，PPARgamma）、共激活因子MED 1、RNA聚合酶II以及表观基因组（H3 K4 me 1/2/3，H3 K9 me 2，H3 K27 me 3，H3 K36 me 3，H3 K27 ac）的基因组结合，以及源自小鼠BAT的永生化前脂肪细胞的脂肪形成期间的染色质开放。我们的数据为理解培养物中棕色脂肪形成的表观基因组调控提供了丰富的资源（Lai B，NAR 2017）。我们正在分析体内脂肪形成过程中的增强子和基因表达。

We are interested in the roles of site-specific methylations on K4, K9, K27, K36 and K79 of histone H3 (H3K4, H3K9, H3K27, H3K36 and H3K79, respectively) in regulation of adipogenesis and PPARgamma. We reported previously that enhancer H3K4me1 methyltransferases MLL3/MLL4 and associated PTIP control the induction of PPARgamma and C/EBPa and are essential for adipogenesis (Cho YW, Cell Metab 2009; Lee JE, eLife 2013; Jang Y, NAR 2019), that H3K9 methyltransferase G9a represses PPARgamma expression and adipogenesis (Wang L, EMBO J 2013), that H3K27 methyltransferase Ezh2 constitutively represses Wnt genes to facilitate adipogenesis (Wang L, PNAS 2010), and that depletion of Nsd2-mediated H3K36 methylation by histone H3.3 mutant H3.3K36M in progenitor cells impairs adipose tissue development and function (Zhuang L, Nat Comm 2018). We also showed that the epigenomic reader Brd4 controls cell identity gene induction and is essential for adipogenesis in vivo (Lee JE, Nat Comm 2017). Together, these findings indicate that epigenomic factors play critical roles in the regulation of adipogenesis (reviewed in Lee JE, MCB 2019). Using conditional knockout mice and preadipocytes, we found surprisingly that although ligand-bound glucocorticoid receptor (GR) accelerates adipogenesis in culture, endogenous GR is dispensable for adipogenesis in culture and in mice (Park Y, MCB 2017a). We also found that KLF4 and Krox20 are dispensable for adipogenesis in culture and in mice (Park Y, MCB 2017b). These unexpected results prompted us to study adipogenesis in vivo. We previously profiled genomic binding of enhancer epigenomic writers (MLL4, CBP), adipogenic TFs (EBF2, C/EBPa, C/EBPb, PPARgamma), coactivator MED1, RNA Polymerase II, as well as epigenome (H3K4me1/2/3, H3K9me2, H3K27me3, H3K36me3, H3K27ac), transcriptome, and chromatin opening during adipogenesis of immortalized preadipocytes derived from mouse BAT. Our data provide a rich resource for understanding epigenomic regulation of brown adipogenesis in culture (Lai B, NAR 2017). We are profiling enhancers and gene expression during adipogenesis in vivo.