Gene Regulatory Networks Controlling Effector and Regulatory T Cell Balance in IBD

项目摘要 IBD中控制效应子和调节性T细胞平衡的基因调控网络。发病机制 炎症性肠病（IBD）的特征在于对肠道微生物群组分的免疫失调。 来自IBD小鼠模型的研究和来自人类的最新遗传数据强调了 免疫调节细胞因子IL-10在维持肠道免疫稳态中的作用。虽然基本的 IL-10的调节功能已被充分确立，控制基因表达的分子机制， 编码IL-10的基因尚不清楚。对于Foxp 3+调节性T细胞尤其如此，Foxp 3+调节性T细胞是主要的调节性T细胞。 肠内免疫调节性IL-10的来源。在使用IL-10转基因报告基因的研究中， 小鼠模型，以探索基于以下表达分离的T细胞转录组之间的差异： IL-10，我们最近发现转录因子Gfi 1是CD 4 T细胞中IL-10表达的中心阻遏物， 细胞这代表了首次鉴定出IL 10基因表达的转录抑制因子，并提示 将Gfi 1募集到IL-10基因座或其他基因座通过以下机制抑制IL-10的表达： 尚未完全定义。更重要的是，我们发现Gfi 1是IL 10基因的泛阻遏物 在所有CD 4 T细胞亚群中表达，但其发挥作用的机制的细节是亚群- 特定.具体而言，初步发现表明，在Foxp 3 + Treg细胞中，存在使用Gfi 1-Blimp 1 转录网络控制IL-10的产生。此外，我们已经确定了细胞因子信号， 诱导Foxp 3 + Treg细胞表达IL-10。本质上，我们发现Treg细胞表达IL-10是一种免疫调节因子。 Iatent，并且需要激活抑制Gfi 1的细胞因子信号以解抑制IL-10表达。这将 解释了为什么T细胞表达IL-10在很大程度上局限于体内平衡的肠道， 对微生物群的反应提供了受控的炎症状态和促炎源 促进“效应子”或表达IL-10的Treg细胞发育的细胞因子。我们假设 肠道中的炎性信号可以克服Foxp 3+调节细胞中Gfi 1介导的IL-10抑制， Gfi 1表达的调节将影响TGF 1在炎症环境中的保护能力。 此外，我们假设在肠道炎症过程中，Gfi 1在CD 4 T细胞中维持致病表型， 通过抑制IL-10表达，重要是抑制结肠炎T细胞中Gfi 1表达， 细胞将致病细胞转化为产生IL-10的保护细胞，从而改善肠道疾病。 在此，我们将定义Gfi 1抑制小鼠和人Treg中IL-10表达的机制。 并将进行原理验证研究，检查T细胞中Gfi 1失调对IBD的影响 发病机制描述外源性细胞因子信号与细胞-内源性Gfi 1和Blimp 1轴的相互作用 通过肠道Treg细胞控制IL-10的表达对于理解体内平衡具有重要意义 这些网络可以预防IBD，并提供新的方法来解除IL-10的抑制，作为一种治疗策略。

PROJECT SUMMARY Gene Regulatory Networks Controlling Effector and Regulatory T Cell Balance in IBD. The pathogenesis of inflammatory bowel disease (IBD) is characterized by immune dysregulation to components of the enteric microbiota. Studies from mouse models of IBD and recent genetic data from humans highlight a critical, non-redundant role for the immunomodulatory cytokine IL-10 in the maintenance of intestinal immune homeostasis. Although the essential regulatory function of IL-10 is well established, molecular mechanisms that control expression of the gene that encodes IL-10 are not well understood. This is particularly the case for Foxp3+ regulatory T cells, the principal source of immunoregulatory IL-10 in the intestines. In studies that have used an IL-10 transgenic reporter mouse model to explore differences between transcriptomes of T cells separated on the basis of expression of IL-10, we recently identified the transcriptional factor, Gfi1, as a central repressor of IL-10 expression in CD4 T cells. This represents the first identification of a transcriptional repressor of Il10 gene expression, and suggests that recruitment of Gfi1 to the Il10 locus or other gene loci inhibits the expression of IL-10 through mechanisms yet to be fully defined. Importantly, we have found that Gfi1 functions as a pan-repressor of Il10 gene expression in all CD4 T cell subsets, but specifics of the mechanism by which it exerts its actions are subset- specific. Specifically, preliminary findings indicate that in Foxp3+ Treg cells there is use of a Gfi1-Blimp1 transcriptional network that controls production of IL-10. Moreover, we have identified cytokine signals that induce the expression of IL-10 in Foxp3+ Treg cells. In essence, we find that IL-10 expression by Treg cells is Iatent, and requires activating cytokine signals that repress Gfi1 to derepress IL-10 expression. This would explain why IL-10 expression by T cells is largely restricted to the intestines at homeostasis, where on-going responses to the microbiota provide a state of controlled inflammation and a source of pro-inflammatory cytokines that promote development of “effector,” or IL-10–expressing Treg cells. We hypothesize that inflammatory signals in the gut can override Gfi1-mediated IL-10 repression in Foxp3+ regulatory cells and that modulation of Gfi1 expression will impact the protective capabilities of Tregs in an inflammatory environment. Further, we hypothesize that during intestinal inflammation, Gfi1 maintains a pathogenic phenotype in CD4 T effector cells by suppressing IL-10 expression and importantly, that inhibition of Gfi1 expression in colitic T cells will convert pathogenic cells to IL-10–producing protective cells, thereby ameliorating intestinal disease. Herein, we will define mechanisms by which Gfi1 represses expression of IL-10 in mouse and human Treg cells and will perform proof-of-principle studies that examine the impact of Gfi1 dysregulation in T cells on IBD pathogenesis. Delineating the interplay of extrinsic cytokine signals with the cell-intrinsic Gfi1 and Blimp1 axis to control IL-10 expression by intestinal Treg cells has important implications for understanding homeostatic networks that prevent IBD and offers novel approaches to de-repress IL-10 as a therapeutic strategy.