Autoimmunity-associated genes in new rat models: validation of human GWAS genes

描述(由申请人提供)：我们知识上的差距：最近，发现了许多有可能引发或延续自身免疫性疾病的遗传位点，其中许多是通过全基因组关联研究(GWAS)发现的。然而，GWAS的结果有时很难解释，匿名SNP关联的效用受到了质疑。数量性状基因座(QTL)和GWAs的基因需要验证和测试，以确定组织和它们发挥作用的关键功能途径。有一个优秀的动物对应物来测试关于非MHC基因如何控制自身免疫的假说，而不受人类研究的伦理和实际考虑的影响，这将是有利的。有效的啮齿动物模型是这样的：(1)在同一疾病中显示出需要一个易感等位基因，(2)候选基因的表达或编码序列存在差异，以便可以比较抗性和易感等位基因，(3)具有可测量的基因与环境和基因之间的相互作用，这可能是促进人类和啮齿动物群体自身免疫所必需的。我们建议的模型满足这些标准。新颖性和风险：1型糖尿病(T1D)是一种T细胞介导的自身免疫性疾病，GWA已经发现了18种显著的非MHC促进糖尿病的关联。在我们的新的T1D大鼠模型中，我们对病毒和TLR激动剂的暴露做出了反应，诱导了T1D，该模型具有出色的临床保真度和对环境扰动蚂蚁的绝对依赖。我们已经将两个高度显著的大鼠QTL定位到包含两个人类GWAS候选基因同源基因的区域：Diubiquitin(UBD或FAT10)和UBASH3A。该模型满足上述所有三个标准，有可能研究这些基因在糖尿病诱发中的作用。风险在于，在糖尿病的发生过程中，这两个物种都不需要与疾病相关的UBD或UBASH3A等位基因，而且人类和大鼠的定位项目都给出了两个错误的候选基因。潜在的突破/与使命的相关性：这项工作将探索UBD和/或UBASH3A如何创造一个有利于糖尿病发病的环境，以应对易感大鼠的病毒感染，并可能提供一个忠实的模型，说明人类同源基因如何做同样的事情。这两个候选基因都在泛素途径中发挥作用，泛素途径已经与T淋巴细胞激活有关，而且在胰腺中也发现了UBD转录本。一个重要的结果将表明，病毒后普遍存在的增强的关键T细胞或β细胞调节通路成员的降解可以导致T1D。目的1.在重组同源基因大鼠中验证UBD和UBASH3A是T1D候选基因的假设。目的2：确定病毒感染后UBD和/或UBASH3A基因表达增强是否为糖尿病表型的基础。确定人类UBD启动子，如大鼠UBD启动子，是否在体外报告试验中显示出启动子活性的等位基因差异。目的3.通过混合配型新生儿T细胞过继转移和T1D病毒诱导，确定两个大鼠糖尿病基因座启动T1D的组织。 公共卫生相关性：自身免疫是一个严重的公共卫生问题，影响着近2000万美国居民。1型自身免疫性糖尿病(T1D)的患病率正在增加，发病时间正在减少；美国青年中出现新病例的比率为1/600。在环境因素的背景下，许多基因都是T1D的易感基因。我们的建议旨在发展一种病毒诱导的T1D大鼠模型，在该模型中，我们定位了两个自身免疫破坏胰岛β细胞所需的基因。每种药物都有人类治疗糖尿病的同义词。这一新的大鼠模型将允许一种新的方法来探索和研究这些基因，并基于它们共享的泛素和途径以及T细胞定位探索潜在的治疗方法。

DESCRIPTION (provided by applicant): Gaps in our knowledge: Recently, numerous genetic loci with the potential to initiate or perpetuate auto- immune disease have been detected, many of them found by genome-wide association studies (GWAS). However, GWAS results are sometimes difficult to interpret, and the utility of anonymous SNP association has been questioned. Genes underlying quantitative trait loci (QTL) and GWAS need verification and testing to identify the tissue and the critical functional pathways in which they act. It would be advantageous to have an excellent animal counterpart to test hypotheses about how non-MHC genes control autoimmunity unimpaired by the ethical and practical considerations of human research. Effective rodent models would be those that: (1) display the need for a susceptible allele at a GWAS homologue in the same disease, (2) have variation in expression or coding sequence of the candidate gene, so that resistant and susceptible alleles can be compared, and (3) have measurable gene-by-environment and gene-by-gene interaction that is likely necessary to promote autoimmunity in both the human and rodent populations. Our proposed model fulfils those criteria. Novelty and Risk: Type 1 diabetes (T1D) is a T cell mediated autoimmune disease, and >18 significant non- MHC diabetes-promoting associations have been discovered by GWAS. In our novel rat model of T1D with excellent clinical fidelity and an absolute dependence on environmental perturb ants, we induce T1D in response to exposure to viruses and TLR agonists. We have mapped two highly significant rat QTL to regions containing two orthologues of human GWAS gene candidates: diubiquitin (UBD or FAT10) and UBASH3A. This model meets all three criteria above for potential to study how these genes act in diabetes induction. The risk is that neither species requires a disease-linked allele of UBD or UBASH3A in diabetogenesis, and that both human and rat mapping projects have given two incorrect candidate genes. Potential breakthroughs/relevance to mission: This work will explore the manner in which UBD and/or UBASH3A creates an environment conducive to the onset of diabetes in response to viral infection in susceptible rats, and could provide a faithful model of the way the human orthologues do the same thing. Both these candidates function in the ubiquitin pathway, already implicated in T lymphocyte activation, and the UBD transcripts are also found in the pancreas. One important outcome would be to show that enhanced post-viral ubiquity-mediated degradation of key T cell or beta-cell regulatory pathway members can lead to T1D. Aim 1. Test the hypothesis that UBD and UBASH3A are T1D candidate genes in recombinant congenic rats. Aim 2: Determine if heightened UBD and/or UBASH3A gene expression after virus infection underlie the diabetes phenotype. Determine if human UBD promoters, like the rat UBD promoter, show allelic differences in promoter activity in an in vitro reporter assay. Aim 3. Determine the tissue in which the two rat diabetes loci act to initiate T1D, with mix-and-match neonatal adoptive transfer of T cells and viral induction of T1D. PUBLIC HEALTH RELEVANCE: Autoimmunity is a serious public health issue that affects nearly 20 million US residents. Type 1 autoimmune diabetes (T1D) is increasing in prevalence and decreasing in time-to-onset; new cases appear at a rate of 1/600 in US youth. Numerous genes predispose to T1D in the context of environmental factors. Our proposal is designed to develop a rat model of virus-induced T1D in which we have mapped two genes required for autoimmune destruction of the pancreatic beta cells. Each has a human diabetes-modifying orthologue. This novel rat model will allow a fresh approach to explore and study these genes and probe potential therapies 9 based on their shared ubiquitin and pathway and T cell localization.