E2A/HEB TRANSCRIPTION FACTORS IN T CELL DEVELOPMENT

描述（由申请人提供）：产生多样化和自我耐受的T细胞库是适应性免疫的主要基础。T细胞在胸腺中的发育导致连续产生表达α / β T细胞受体（TCR）的CD4或CD8 T细胞和少量表达γ / δ TCR的γ / δ T细胞。每个发育中的T细胞的命运严重依赖于TCR基因在重排和TCR介导选择中的选择。大多数γ / δ T细胞在祖细胞完全进入α / β谱系之前就发育了。即使不能产生功能性的α / β TCR， α / β谱系的T细胞祖细胞也很少切换到γ / δ谱系。这种单向发展在很大程度上是由成功表达的TCR链的正反馈信号驱动和强制的。因此，基于TCR的选择是T细胞发育的关键检查点。由结构和功能相关的E2A和HEB基因编码的转录因子已被证明参与TCR基因重排和TCR介导的选择。我们在之前的资助周期中对E2A和HEB及其抑制剂Id3的研究有助于目前对T细胞发育各个阶段的转录网络的理解。对携带目标突变的小鼠的分析导致了两个与当前建议直接相关的最新发现。首先，我们的研究暗示了E2A和HEB及其抑制剂Id3在控制γ / δ与α / β谱系发育中的调节作用。其次，E2A和HEB的条件失活揭示了E2A和HEB在TCR1基因重排完成之前阻断T细胞成熟的必要作用。基于这些新发现，我们在本提案中提出了两个具体目标。目的1是研究α / β谱系细胞中抑制γ / δ谱系命运的调控机制。目的2是研究E2A和HEB在TCR表达之前抑制T细胞成熟的机制。这些研究的结果将直接影响我们对转录网络的理解，这些转录网络指导着正确的谱系分化和选择功能性和自我耐受的T细胞。我们在过去资助周期中的研究表明，这种转录网络的遗传扰动直接导致自身免疫性疾病和免疫功能失调。目前的建议应继续提供有关人类自身免疫性疾病的原因的见解。公共卫生相关性：本研究是我们在过去8年中对E2A/HEB在T淋巴细胞发育中的功能进行的卓有成效的研究的延续。我们为E2A/HEB转录因子如何控制T细胞发育过程中的分化、增殖和细胞死亡提供了重要的遗传基础。此外，我们的研究还建立了人类自身免疫性疾病（如干燥综合征）的重要动物模型。在目前的提案中，我们将重点研究E2A/HEB协调T细胞受体基因重排和T细胞选择事件的机制。拟议的研究应提供遗传和分子基础的生产多样化，但非自身反应性T细胞群。

DESCRIPTION (provided by applicant): Generation of a diversified and self-tolerant T cell repertoire constitutes a major foundation of adaptive immunity. T cell development in the thymus results in a continuous generation of CD4 or CD8 T cells expressing alpha/beta T cell receptor (TCR) and a small number of gamma/delta T cells expressing gamma/delta TCR. The fate of each developing T cell is critically dependent on the choice of TCR gene in rearrangement and TCR mediated selection. Most gamma/delta T cells develop early before progenitor cells fully commit to the alpha/beta lineage. T cell progenitors committed to the alpha/beta lineage rarely switch to the gamma/delta lineage even if they fail to produce a functional alpha/beta TCR. This unidirectional development is largely driven and enforced by positive feed back signals from a successfully expressed TCR chain. Thus, TCR based selections serve as critical checkpoints in T cell development. Transcription factors encoded by the structurally and functionally related E2A and HEB genes have been shown to participate in both TCR gene rearrangement and TCR mediated selection. Our own studies of E2A and HEB and their inhibitor Id3 from the previous funding cycles have contributed to the current understanding of this transcriptional network at various stage of T cell development. Analysis of mice carrying targeted mutations has led to two most recent discoveries which are directly relevant to the current proposal. First, our study implicated a regulatory role for E2A and HEB and their inhibitor Id3 in controlling gamma/delta vs. alpha/beta lineage development. Second, conditional inactivation of both E2A and HEB has revealed a necessary role for E2A and HEB in blocking T cell maturation prior to completion of TCR1 gene rearrangement. Based on these novel findings, we propose two specific aims in the current proposal. Aim 1 is to investigate the regulatory mechanism suppressing the gamma/delta lineage fate among cells committed to the alpha/beta lineage. Aim 2 is to investigate the mechanism by which E2A and HEB suppress T cell maturation prior to TCR expression. Outcomes of these studies should directly impact our understanding of the transcriptional network guiding proper lineage differentiation and selection of functional and self-tolerant T cells. Our study in the past funding cycles has demonstrated that genetic perturbation of this transcriptional network directly causes autoimmune disease and dysregulation of immune function. Current proposal should continuously provide insights into the cause of autoimmune disease relevant to humans. Public Health Relevance: The proposed study is a continuation of our fruitful research on function of E2A/HEB in T lymphocyte development for the past 8 years. We have provided crucial genetic basis for how E2A/HEB transcription factors control differentiation, proliferation, and cell death during T cell development. In addition, our study has led to establishment of important animal models for human autoimmune diseases such as Sjogren's syndrome. In the current proposal, we will focus our research on understanding the mechanism by which E2A/HEB coordinate T cell receptor gene rearrangement and T cell selection events. The proposed study should provide both genetic and molecular basis for the production of a diverse yet non-autoreactive T cell population.