Analyzing The Joint Susceptibility Genes for Autoimmune Thyroiditis and Diabetes

描述(申请人提供)：自身免疫性甲状腺疾病(AITD)和1型糖尿病(T1D)经常发生在同一个家庭和同一个人身上。当AITD T1D发生在同一个体中时，表型被认为是多腺性综合征3型(APS3变体[APS3v])的变体。我们的目标是：(1)识别和表征AITD和T1D的联合易感基因，以及(2)剖析它们致病的机制。在过去的资助期间，我们在这些目标上取得了实质性的进展，包括：(1)我们完成了第一次报道的AITD和T1D家系的基因组扫描，定位了AITD和T1D共同的新基因，并在连锁基因座上确定了AITD和T1D的3个联合基因；(2)确定CTLA-4、PTPN22、Insulin VNTR是APS3v(AITD T1D)表型的易感基因；(3)发现了对APS3v的发育至关重要的独特的HLA-DR口袋氨基酸特征，并确定了该口袋的三维结构；(4)用AITD T1D(APS3v)组装了一个约700人的数据集，为我们在这个子集进行大规模关联研究提供了力量；以及(5)剖析了AITD基因(TG、CD40和TSHR)变异易患疾病的机制。我们建议在这些发现的基础上继续我们的假设，即AITD和T1D的联合病因取决于几个基因之间的遗传和生物相互作用。我们的具体目标是：特定目标1：鉴定和鉴定与独特的人类白细胞抗原DR口袋结合的甲状腺球蛋白(TG)、TPO、胰岛素和GAD65多肽，我们发现这对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APS3v相关口袋结构的多肽；以及(2)生化和质谱学实验来确定与口袋结合的多肽。具体目的2：剖析CTLA-4和FOXP3变异体易感APS3v的机制：(1)CTLA-4：我们将测试3‘UTR微卫星是否通过降低CTLA-4 mRNA的稳定性而易感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)n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)新的易感基因：(1)精细定位：利用密集分布的SNPs对2p上的一个主要基因座进行精细定位。(2)亚集分析：我们将利用我们的APS3v患者大数据集和4000名种族匹配的对照的可用基因型别，对APS3v患者的亚集进行全面的关联研究。(3)基因-基因相互作用：将对已识别的基因进行基因-基因相互作用分析。目前的建议直接建立在前一次赠款期间获得的知识基础上，旨在剖析导致AITD和T1D之间强烈关联的分子途径。这将有助于更好地理解AITD和T1D以及APS3v的共同病因，并可能促进基于机制的治疗模式的发展，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，包括桥本氏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个家庭和同一个人中，最有可能是由于共同的遗传易感性。我们研究的目的是识别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，并研究它们导致这两种疾病的机制。了解导致甲状腺自身免疫和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内预测疾病，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