A Trim28-ERV axis drives phenotypic variation in obesity

修改项目摘要/摘要部分 来自双胞胎和近交动物模型的估计表明，高达50%的代谢疾病异质性是由于遗传或环境以外的原因。我们之前发现Trim 28是非遗传、非环境表型异质性的主要调节因子;证明Trim 28缓冲了同基因Trim 28 +/D9小鼠中独特的（非遗传性）表观遗传肥胖;并在人类肥胖中鉴定了可比较的TRIM 28相关mRNA表达特征。处于肥胖、表观遗传学“ON”端的个体的特征在于Trim 28敏感基因座的失调，包括内源性逆转录病毒（ERV）。Trim 28-通常与KZFP相互作用，使ERV在整个发育过程中保持稳定，完全沉默的状态。然而，ERV的一个子集部分逃脱这种沉默，并成为VM-ERV的甲基化，这转化为可变水平的抑制/激活，随后在相邻的基因表达的变异性，并最终表型变异。我们的初步数据表明，VM-ERV的序列内容，使他们能够结合的锌指-CxxC（ZF-CxxC）结构域含有蛋白质，从而保护这些基因座甲基化。我们假设VM-ERV基因座的激活与沉默是由KZFP/Trim 28和ZF-CxxC结合之间的竞争控制的，并且TRIM 28敏感的VM-ERV表达是无法解释的表型变异和代谢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ERVs的表观基因组特征，以确定定义VM-ERVs的表观基因组和基因组特征。在目标2中，我们将分析特异性ZF-CxxC蛋白（CFP 1和TET 1）的结合，以证明随着Trim 28水平降低，这些蛋白获得竞争性结合优势，并证明ZF-CxxC - KZFP/Trim 28竞争触发VM-ERV的表观遗传变异性。在目标3中，我们将确定VM-ERV激活是否与代谢疾病异质性相关。我们希望这个项目将确定Trim 28/ZF-CxxC竞争作为一种新的机制，在ERV的变量沉默，并提供研究界的目标蛋白和途径的全面清单，研究和开始了解VM-ERV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.