TOX, A Novel Regulator of Thymocyte Selection

描述（由申请人提供）：越来越清楚的是，胸腺的工作比最初认识到的更复杂。该器官不仅是CD4和CD8 T细胞的产生者，而且也是自然杀伤T（NKT）细胞、上皮内T淋巴细胞、调节性T（Treg）细胞和先天性CD8 T细胞的高度特化谱系的发育场所。控制这些不同的T细胞亚系从共同的前体分化的详细分子机制仍有待确定。在这里，我们专注于TOX（胸腺细胞选择相关的HMG盒蛋白）在这种情况下，在我们的实验室中首次确定为胸腺选择事件的调节器的核DNA结合蛋白的作用。 我们生产了TOX缺陷小鼠，证明TOX是典型CD4 T细胞谱系以及NKT和Treg细胞发育所需的。在这些突变动物中受影响的T细胞发育的特定阶段的抑制以前没有报道，允许对该过程的新见解。此外，我们发现TOX在胸腺外发挥作用，包括在NK细胞发育和淋巴结器官形成中的强制性作用。我们在这里提出了三个具体的目标来描绘的作用和机制的TOX在免疫系统的发展。首先，我们将研究TOX和调节胸腺中的CD4和ThPOK表达之间的关系，后者是一种占主导地位的CD4谱系定型因子。此外，我们提出了一种新的方法来确定参与建立CD4谱系基因程序的TOX依赖性基因，并将比较TOX在不同T细胞谱系发育中的作用。其次，我们将分析TOX在淋巴结器官发生发育中的作用，重点是TOX调节淋巴组织诱导细胞发育的潜力。我们还在培养系统中复制了在不存在TOX的情况下对NK细胞发育的抑制。我们提出了详细的分析TOX在这种情况下的作用，包括是否TOX可能发挥作用，以调节另一个核因子，共享一些功能特性与TOX。第三，我们提出了最先进的方法，以确定直接的基因靶点和蛋白结合伙伴的TOX，在体内的CD4 T细胞的发展。 TOX在啮齿动物和人类之间高度保守，其表达模式也是如此。因此，这些研究也应该提供对人类免疫系统工作的深入了解。TOX定义了一个小的蛋白质亚家族，包括三个其他成员，其中一个被认为是乳腺癌易感基因座，而TOX本身在一些癌细胞系和肿瘤中高度表达。因此，了解TOX的作用机制可能会影响人类健康和疾病。

DESCRIPTION (provided by applicant): It has become increasingly clear that the workings of the thymus include greater complexity than first appreciated. Not only is this organ a generator of CD4 and CD8 T cells, but it is also a site for development of highly specialized lineages of natural killer T (NKT) cells, intraepithelial T lymphocytes, regulatory T (Treg) cells, and innate-like CD8 T cells. The detailed molecular mechanisms that control the differentiation of these distinct T cell sublineages from common precursors remain to be determined. Here we focus on the role of TOX (thymocyte selection-associated HMG box protein) in this context, a nuclear DNA-binding protein first identified in our laboratory as a regulator of thymic selection events. We produced TOX-deficient mice, demonstrating that TOX is required for development of the canonical CD4 T cell lineage as well as NKT and Treg cell development. Inhibition of the specific stage of T cell development that is affected in these mutant animals has not been reported previously, allowing novel insights into the process. In addition, we have found that TOX plays roles outside the thymus, including an obligatory role in NK cell development and lymph node organogenesis. We propose here three specific aims to delineate the role and mechanism of action of TOX in development of the immune system. First, we will investigate the relationship between TOX and regulation of CD4 and ThPOK expression in the thymus, the latter a dominant CD4 lineage commitment factor. In addition, we propose a novel approach to identify TOX-dependent genes involved in establishment of the CD4 lineage gene program, and will compare the role of TOX in development of different T cell lineages. Second, we will analyze the role of TOX in development of lymph node organogenesis, focusing on the potential for TOX to regulate lymphoid tissue inducer cell development. We also have replicated the inhibition of NK cell development in the absence of TOX in a culture system. We propose detailed analysis of the role for TOX in this context, including whether TOX might function to regulate another nuclear factor that shares some functional properties with TOX. Third, we propose state-of-the-art approaches to identify direct gene targets and protein binding partners of TOX, in an in vivo context of CD4 T cell development. TOX is highly conserved between rodents and humans, as is its expression pattern. Thus, these studies should provide insight into workings of the human immune system as well. TOX defines a small protein subfamily that includes three other members, one of which has been implicated as a breast cancer susceptibility locus, while TOX itself is highly expressed in some cancer cell lines and tumors. Understanding the mechanism of action of TOX is therefore likely to impact both human health and disease.