A Trim28-ERV axis drives phenotypic variation in obesity

修改后的项目摘要/摘要部分 来自双胞胎和近亲交配动物模型的估计表明，高达50%的代谢性疾病异质性是由遗传或环境以外的因素造成的。我们之前发现，Trim28是非遗传、非环境表型异质性的主要调节因子；证明了Trim28可以缓冲等基因Trim28+/D9小鼠中独特的(双稳态)表观遗传肥胖；并在人类肥胖中发现了类似的TRIM28相关mRNA表达特征。处于肥胖、表观遗传学“ON”一端的个体的特征是Trim28敏感基因座调节失调，包括内源性逆转录病毒(ERV)。Trim28-通常与KZFP相互作用，以在整个开发过程中保持ERV处于稳定、完全静音的状态。然而，ERV的一部分子集部分逃脱了这种沉默，变得可变甲基化(Vm-ERV)，这转化为不同水平的抑制/激活，随后邻近基因表达的可变性，最终表型差异。我们的初步数据表明，Vm-ERV具有序列内容，允许它们与含锌指CxxC(ZF-CxxC)结构域的蛋白质结合，从而保护这些基因座不受甲基化的影响。我们假设Vm-ERV基因座的激活和沉默是由KZFP/Trim28和ZF-CxxC结合之间的竞争控制的，并且TRIM28敏感的Vm-ERV表达是原因不明的表型变异和代谢性疾病异质性的重要驱动因素。我们将通过三个独立的目标来检验这些假设。在目标1中，我们将定义肝细胞和脂肪细胞中ERV的表观基因组学特征，以确定定义Vm-ERV的表观基因组学特征。在目标2中，我们将分析特定的ZF-CxxC蛋白(CFP1和TET1)的结合情况，以证明这些蛋白随着Trim28水平的降低而获得竞争结合优势，并证明ZF-CxxC-KZFP/Trim28竞争触发了Vm-ERV的表观遗传变异。在目标3中，我们将确定VM-ERV的激活是否与代谢性疾病的异质性有关。我们希望这个项目将确定Trim28/ZF-CxxC竞争是一种控制ERV可变沉默的新机制，并为研究团体提供一个全面的靶蛋白和途径清单，以研究和开始了解VM-ERV调节失调如何触发和/或影响复杂的疾病病因。

Modified Project Summary/Abstract Section Estimates from twin and inbred animal models suggest that up to 50% of metabolic disease heterogeneity is due to something other than genetics or the environment. We previously discovered that Trim28 is a master regulator of non-genetic, non-environmental phenotypic heterogeneity; demonstrated that Trim28 buffers against a unique (bistable) epigenetic obesity in isogenic Trim28+/D9 mice; and identified a comparable TRIM28-associated mRNA expression signature in human obesity. Individuals at the obese, epigenetically “ON” end of the spectrum are characterized by dysregulation of Trim28-sensitive loci, including endogenous retroviruses (ERVs). Trim28-normally interacts with KZFPs to keep ERVs in a stable, fully silenced state throughout development. However, a subset of ERVs partially escape this silencing and become variably methylated (VM-ERVs), which translates into variable levels of repression/activation, subsequent variability in neighboring gene expression, and ultimately phenotypic variation. Our preliminary data indicate that VM-ERVs have sequence content allowing them to be bound by Zinc-Finger-CxxC (ZF-CxxC) domain containing proteins, thereby protecting these loci from methylation. We hypothesize that activation vs silencing at VM-ERV loci is controlled by a competition between KZFP/Trim28 and ZF-CxxC binding, and that TRIM28-sensitive VM-ERV expression is a significant driver of unexplained phenotypic variation and metabolic disease heterogeneity. We will test these hypotheses through three independent Aims. In Aim 1, we will define the epigenomic characteristics of ERVs in hepatocytes and adipocytes to identify the epigenomic and genomic features that define VM-ERVs. In Aim 2, we will profile binding of specific ZF-CxxC proteins (CFP1 and TET1) to prove that these proteins gain a competitive binding advantage as Trim28 levels are reduced and demonstrate that ZF-CxxC – KZFP/Trim28 competition triggers epigenetic variability at VM-ERVs. In Aim 3, we will determine if VM-ERV activation is coupled to metabolic disease heterogeneity. We expect this project will identify Trim28/ZF-CxxC competition as a novel mechanism governing the variable silencing at ERVs and provide the research community with a comprehensive list of target proteins and pathways to study and begin understanding how VM-ERV dysregulation triggers and/or influences complex disease etiology.