Analyzing The Joint Susceptibility Genes for Autoimmune Thyroiditis and Diabetes

自身免疫性甲状腺疾病（AITD）和1型糖尿病（T1D）经常发生在同一家族和同一个体中。当AITD+T1D发生在同一个体时，该表型被认为是3型多腺综合征（APS3变体[APS3v]）的一种变体。我们的目标是：(1)识别和表征AITD和T1D的联合易感基因，(2)剖析它们致病的机制。在上一个资助期间，我们在这些目标方面取得了实质性进展，包括：(1)我们完成了首次报道的AITD和T1D家族的基因组扫描，绘制了AITD和T1D共有的新位点，并在连锁位点中确定了AITD和T1D的3个联合基因；(2)确定ctla -4、PTPN22、胰岛素VNTR是APS3v （AITD+T1D）表型的易感基因；(3)发现了一个独特的HLA-DR口袋氨基酸特征，这对APS3v的发展至关重要，并确定了该口袋的三维结构；(4)建立了约700名AITD+T1D （APS3v）个体的数据集，为该子集的大规模关联研究提供了动力；(5) AITD基因（Tg、CD40和TSHR）变异导致疾病易感性的解剖机制。我们建议在这些发现的基础上继续我们的假设，即AITD和T1D的联合病因学取决于几个基因之间的遗传和生物学相互作用。我们的具体目标是：具体目标1：鉴定和表征甲状腺球蛋白（Tg）、TPO、胰岛素和GAD65肽，这些肽与我们发现的独特的HLA-DR口袋结合，对APS3v的发展至关重要。我们将使用：(1)分子建模和生物信息学研究来预测最适合apsv相关口袋结构的肽；(2)通过生化和质谱实验鉴定与口袋结合的肽。具体目标2：剖析CTLA-4和FOXP3变异体易患APS3v的机制：(1)CTLA-4：我们将通过降低CTLA-4 mRNA的稳定性来测试3'UTR微卫星是否易患APS3v。(2) FOXP3：我们将通过改变FOXP3的选择性剪接来研究内含子5 （TC）微卫星重复是否会增加APS3v的风险。具体目标3：精细定位和鉴定APS3v （AITD+T1D）的新易感基因：(1)精细定位：2p上的一个主要位点将使用密集间隔的snp和鉴定的基因进行精细定位。(2)亚群分析：我们将对APS3v患者亚群进行全面的关联研究，使用我们的APS3v患者大数据集和4000个种族匹配的对照组的现有基因型。(3)基因-基因互作：对鉴定出的基因进行基因-基因互作分析。目前的提案直接建立在上一个资助期获得的知识基础上，旨在剖析导致AITD和T1D之间强关联的分子途径。这将有助于更好地了解AITD和T1D以及APS3v的共同病因，并可能促进基于机制的治疗方式的发展，如HLA-DR口袋阻断或CTLA-4激活。公共卫生相关性：自身免疫性甲状腺疾病，包括桥本甲状腺炎和格雷夫斯病，通常与1型（青少年）糖尿病一起发生在同一家族和同一个体中，很可能是由于共同的遗传易感性。我们的研究目的是鉴定和表征自身免疫性甲状腺疾病和1型糖尿病的联合易感基因，并研究它们引起这两种疾病的机制。了解导致甲状腺自身免疫与1型糖尿病之间强烈关联的机制将使我们不仅能够在家庭中预测疾病，而且还可以制定合理的，基于机制的治疗和预防策略

DESCRIPTION (provided by applicant): Autoimmune thyroid diseases (AITD) and type 1 diabetes (T1D) frequently occur within the same family and in the same individual. When AITD+T1D occur in the same individual, the phenotype is considered a variant of the polyglandular syndrome type 3 (APS3 variant [APS3v]). Our goals are: (1) to identify and characterize the joint susceptibility genes for AITD and T1D, and (2) to dissect the mechanisms by which they cause disease. During the last grant period, we have made substantial progress toward these goals, including: (1) We completed the first reported genome scan in families with AITD & T1D, mapped new loci common to AITD & T1D, and identified 3 joint genes for AITD & T1D in linked loci; (2)Determined thatCTLA-4, PTPN22, Insulin VNTR are susceptibility genes for the APS3v (AITD+T1D) phenotype; (3) Discovered a unique HLA-DR pocket amino acid signature that was critical for the development of APS3v and determined the 3-D structure of that pocket; (4) Assembled a dataset of ~ 700 individuals with AITD+T1D (APS3v), giving us power for large scale association studies in this subset; and (5) Dissected mechanisms by which variants in AITD genes (Tg, CD40, & TSHR) predispose to disease. We propose to build on these findings to pursue our hypothesis that the joint etiology of AITD & T1D depends on genetic and biological interactions between several genes. Our specific aims are: Specific Aim 1: To identify & characterize thyroglobulin (Tg), TPO, insulin, and GAD65 peptides that bind to the unique HLA-DR pocket that we found to be critical for the development of APS3v. We will use: (1) molecular modeling and bioinformatics studies to predict peptides that best fit the structure of the APS3v-associated pocket; and (2) biochemical and mass spectrometry experiments to identify peptides that bind to the pocket. Specific Aim 2: To dissect the mechanisms by which CTLA-4 & FOXP3 variants predispose to APS3v: (1) CTLA-4: we will test whether a 3'UTR microsatellite predisposes to APS3v by lowering CTLA-4 mRNA stability. (2) FOXP3: we will examine whether an intron 5 (TC)n microsatellite repeat confers risk for APS3v by altering the alternative splicing of FOXP3. Specific Aim 3: To fine map and identify new susceptibility genes for APS3v (AITD+T1D): (1) Fine mapping: A major locus on 2p will be fine mapped using densely spaced SNPs & the gene identified. (2) Subset analysis: We will perform a comprehensive association study on the subset of APS3v patients, using our large dataset of APS3v patients and available genotypes on 4000 ethnically matched controls. (3) Gene-gene interaction: genes identified will be analyzed for gene-gene interaction. The current proposal builds directly on the knowledge gained in the previous grant period, and aims to dissect the molecular pathways causing the strong association between AITD and T1D. This will lead to better understanding of the common etiology of both AITD & T1D, as well as APS3v, and may facilitate the development of mechanism- based treatment modalities, such as HLA-DR pocket blockade, or CTLA-4 activation. PUBLIC HEALTH RELEVANCE: Autoimmune thyroid diseases, including Hashimoto's thyroiditis and Graves' disease commonly occur together with type 1 (Juvenile) diabetes in the same families and in the same individual, most likely due to shared genetic susceptibility. The goal of our studies is to identify and characterize the joint susceptibility genes for autoimmune thyroid diseases and type 1 diabetes, and to study the mechanisms by which they cause these two diseases. Understanding the mechanisms causing the strong association between thyroid autoimmunity and type1 diabetes will allow us not only disease predictions within families, but also to develop rational, mechanism-based, treatment and prevention strategies