The Role of EOS in Regulatory T-cell Biology.

描述（由申请人提供）：自然发生的以及适应性发展的Foxp3+CD4+调节性T细胞（Treg）是通过抑制异常或过度的免疫反应来维持免疫自身耐受性和免疫稳态的核心。Treg特异性表达转录因子Foxp3，介导CTLA-4和GITR等基因的协同激活，以及白细胞介素-2、IL-17和干扰素-？通常由效应T细胞（Teff）表达。Treg和Teff之间的功能界限并不是绝对的。事实上，Treg和Teff之间的柔韧性可能是生理和病理生理免疫反应的重要组成部分。了解这种功能互换需要了解免疫效应基因在Treg中通常是如何沉默的。尽管对foxp3依赖基因激活机制的了解有所进展，但foxp3依赖基因抑制的分子机制尚未阐明。最近，我们发现Ikaros家族的锌指转录因子Eos是Treg中foxp3依赖性基因沉默的关键介质。Eos直接与Foxp3相互作用，在不影响Foxp3激活基因表达的情况下实现基因沉默。我们进一步证明Eos及其协同抑制因子c端结合蛋白1 （CtBP1）对于Treg中选择性基因沉默的组蛋白修饰和最终启动子甲基化是必需的。在体外和体内实验中，Treg中Eos的敲低可使其丧失抑制免疫反应的能力。我们假设Eos-CtBP-1基因沉默在Treg中是一个高度调控的过程，影响其作为免疫抑制者或效应者的功能。在目前的提案中，我们将进一步探索Treg中Eos-CtBP1基因沉默的代谢和microRNA依赖的调节机制，以及该途径的消融对Treg发育、稳态和适应性免疫反应调节的体内影响。具体来说，我们将1)阐明影响NADH/NAD平衡的代谢刺激在通过CtBP1复合物介导的Eos介导的基因沉默中的作用；2)研究微rna对Treg细胞中Eos表达的调控；3)研究Eos缺失对Treg细胞稳态、分化和适应性Treg细胞发育的影响。

DESCRIPTION (provided by applicant): Naturally occurring as well as adaptively developed Foxp3+CD4+ regulatory T cells (Treg) are central to the maintenance of immunological self-tolerance and immune homeostasis by suppressing aberrant or excessive immune responses. Treg specifically express the transcription factor Foxp3, which mediates the coordinate activation of genes such as CTLA-4 and GITR along with silencing of cytokines such as interleukin-2, IL-17 and interferon-?, that are normally expressed by effector T cells (Teff). The functional boundary between Treg and the Teff they are meant to suppress is not absolute. In fact, the flexibility between Treg and Teff may be an important component to both physiologic and pathophysiologic immune responses. Understanding this functional interchange requires an understanding of how immune effector genes are normally silenced in Treg. Despite progress in understanding mechanisms of Foxp3-dependent gene activation, the molecular mechanism of Foxp3-dependent gene repression has not been elucidated. Recently, we identified Eos, a zinc-finger transcription factor of the Ikaros family, as a critical mediator of Foxp3-dependent gene silencing in Treg. Eos interacts directly with Foxp3 and is necessary for gene silencing without affecting expression of Foxp3 activated genes. We further demonstrated that Eos and its corepressor C-terminal binding protein 1 (CtBP1) are necessary for histone modifications and ultimately promoter methylation involved in selective gene silencing in Treg. Knockdown of Eos in Treg abrogates their ability to suppress immune responses in vitro and in vivo. We hypothesize that Eos-CtBP-1 gene silencing is a highly regulated process in Treg that impacts on their function as suppressors vs. effectors of immunity. In the current proposal, we will further explore metabolic and microRNA dependent mechanisms of regulation of Eos-CtBP1 gene silencing in Treg as well as the in vivo consequences of ablation of this pathway for Treg development, homeostasis and modulation of adaptive immune responses. Specifically, we will 1) Elucidate the role of metabolic stimuli that affect NADH/NAD balance in Eos mediated gene silencing via the CtBP1 complex, 2) Study the regulation of Eos expression in Treg cells by microRNAs and 3) Study the consequences of Eos deletion to Treg cell homeostasis, differentiation and adaptive Treg cell development.