Investigating the role of TET deficiency in promoting T cell expansion and inflammation

摘要 DNA胞嘧啶甲基化（下文中，DNA甲基化）在细胞谱系特化中具有关键作用， 抑制基因组中的重复和转座因子。DNA甲基转移酶将甲基 泰特甲基胞嘧啶双加氧酶通过以下方式引起DNA去甲基化： 将5 mC的甲基氧化成5-羟甲基胞嘧啶（5 hmC）和更高。我们已经证明了泰特- 缺陷细胞类型不仅显示预期的启动子和增强子DNA甲基化增加， 也是基因组异染色质区域DNA甲基化的反常减少。后果 这些分子特征中的一些尚待了解，但在全基因组DNA甲基化中类似的改变， 在癌症和衰老中观察到了这种模式。 通过对诱导表达Cre重组酶的几种小鼠品系的表型研究， 或在免疫/造血细胞类型中的发育，我们发现两个或更多个泰特基因的缺失 在相关细胞类型中，以与细胞谱系变化相关的方式， 承诺.然而，更引人注目的表型是Tet 2/3 fl/fl CD 4Cre小鼠显示出大量的TCR-γ受体。 iNKT细胞的依赖性扩增; Tet 2/3 fl/fl Foxp 3Cre小鼠产生了显性的促炎性细胞因子， 在杂合子雌性小鼠、混合骨髓嵌合体和免疫活性小鼠中观察到的表型 接受者注射来自Tet 2/3 fl/fl Foxp 3Cre小鼠的总CD 4 + T细胞。这种表型明显不同于 这在杂合Foxp 3 +/-雌性和注射Foxp 3缺陷的免疫活性小鼠中观察到 细胞，它们不会产生疾病。在目标1中，我们将讨论显著扩张的潜在机制 Tet 2/3缺陷iNKT细胞的体内过继转移方法和最近开发的细胞培养 在体外重现扩增的系统。在目标2中，我们将询问显性自身免疫性/ Tet 2/3缺陷型调节性T细胞的炎性表型直接或间接地需要减少的DNA 到目前为止，在检查的每种TET缺陷细胞类型中观察到异染色质甲基化。降低的DNA 异染色质中的甲基化导致“异染色质功能障碍”，一种与 自身免疫性/炎症性疾病、癌症、衰老和神经退行性疾病，其源于异常的 转座因子（TE）的表达和导致的DNA损伤。DNA损伤引发“不育 炎症”：RNA和DNA的先天免疫传感途径的激活，随后上调 I型干扰素、干扰素诱导基因和促炎细胞因子（如IL-1b、IL-6、IFNg、IL-17） 我们提出的实验将增加我们对泰特蛋白如何影响T细胞扩增和T细胞增殖的认识。 调节功能。更广泛地说，它们将增强我们对连接泰特的联系的一般理解 自身免疫性/炎症性疾病、克隆性造血、癌前病变、 与炎症、心血管疾病和癌症相关的老年人综合征。

Abstract DNA cytosine methylation (hereafter, DNA methylation) has a critical role in cell lineage specification as well as suppression of repetitive and transposable elements in the genome. DNA methyltransferases attach a methyl group to generate 5-methylcytosine (5mC); TET methylcytosine dioxygenases cause DNA demethylation by oxidizing the methyl group of 5mC to 5-hydroxymethylcytosine (5hmC) and beyond. We have shown that TET- deficient cell types display not only the expected increase in DNA methylation at promoters and enhancers, but also a paradoxical decrease in DNA methylation in heterochromatic regions of the genome. The consequences of these molecular features remain to be understood, but similar alterations in genome-wide DNA methylation patterns have been observed in cancer and aging. By studying the phenotypes of several mouse strains in which Cre recombinase was expressed either inducibly or developmentally in immune/ hematopoietic cell types, we showed that deletion of two or more Tet genes skewed cell lineage commitment in the relevant cell type, in a manner that correlated with changes in cell lineage commitment. More striking phenotypes, however, were that Tet2/3 fl/fl CD4Cre mice displayed massive TCR- dependent expansion of iNKT cells; and that Tet2/3 fl/fl Foxp3Cre mice developed a dominant proinflammatory phenotype observed in heterozygous female mice, in mixed bone marrow chimaeras, and in immunocompetent recipients injected with total CD4+ T cells from Tet2/3 fl/fl Foxp3Cre mice. This phenotype differs markedly from that observed in heterozygous Foxp3+/- females and in immunocompetent mice injected with Foxp3-deficient cells, which do not develop disease. In Aim 1, we will address the mechanisms underlying the striking expansion of Tet2/3-deficient iNKT cells by using adoptive transfer approaches in vivo and recently-developed cell culture systems that recapitulate the expansion in vitro. In Aim 2, we will ask whether the dominant autoimmune/ inflammatory phenotype of Tet2/3-deficient T regulatory cells requires, directly or indirectly, the decreased DNA methylation in heterochromatin observed in every TET-deficient cell type examined so far. Decreased DNA methylation in heterochromatin results in “heterochromatin dysfunction”, an aberrant cellular condition linked to autoimmune/ inflammatory disorders, cancer, aging, and neurodegenerative diseases, that stems from aberrant expression of transposable elements (TEs) and resulting DNA damage. DNA damage provokes “sterile inflammation”: activation of innate immune sensing pathways for RNA and DNA with consequent upregulation of type I interferons, interferon-induced genes and proinflammatory cytokines (e.g. IL-1b, IL-6, IFNg, IL-17) Our proposed experiments will add to our knowledge of how TET proteins influence T cell expansion and T regulatory function. More broadly, they will enhance our general understanding of the links connecting TET deficiency and TE expression with autoimmune/ inflammatory diseases, clonal hematopoiesis, a premalignant syndrome of older individuals associated with inflammation and cardiovascular disease, and cancer.