Determining the mechanism of IFIH1 disease-associated variants on beta-cell and immune responses in Type 1 diabetes

项目总结/摘要 1型糖尿病（T1 D）是一种多因素自身免疫性疾病，需要遗传易感性， 以及环境触发因素，如病毒感染，在引发疾病发作。1例病毒感染 与T1 D高度相关的是柯萨奇病毒B（CVB）血清型。感知CVB是 由黑素瘤分化相关蛋白5（MDA 5）介导，所述MDA 5是dsRNA的胞质传感器， 由IFIH 1基因编码。刺激MDA 5信号通路激活了 转录因子IRF 3和NF-κB p65，它们诱导I型IFN的合成， 自分泌信号启动抗病毒转录程序。单核苷酸多态性 IFIH 1基因中的SNP，如rs 1990760，其导致非同义突变， 将946位的丙氨酸变为苏氨酸，与T1 D风险增加高度相关。 在人PBMC和小鼠中的研究已经证明，A946 T SNP导致增加的细胞增殖。 对病毒配体的敏感性和随后更强的下游IFN应答。巨噬细胞具有 先前已显示在T1 D起始中起重要作用，然而，β细胞对 病毒感染也很重要。我们的中心假设是T1 D相关的SNP导致 胰岛驻留巨噬细胞免疫反应和β细胞炎症反应加剧， CVB 3感染，导致自身免疫的启动。这将用单核细胞进行测试- 衍生的巨噬细胞和树突细胞以及诱导的多能干细胞， 来自健康供体和T1 D患者的人胰腺β细胞，其针对IFIH 1进行基因分型 导致T1 D易感性和耐药性的SNP。

Project Summary/Abstract Type 1 diabetes (T1D) is a multifactorial autoimmune disease that requires genetic susceptibility as well as environmental triggers such as viral infections in triggering disease onset. One viral infection that is highly correlated with T1D is the Coxsackievirus B (CVB) serotype. Sensing of CVB is mediated by the melanoma differentiation-associated protein 5 (MDA5), a cytosolic sensor of dsRNA, which is encoded by the IFIH1 gene. Stimulation of the MDA5 signaling pathway activates the transcription factors IRF3 and NF-κB p65, which induce Type I IFNs synthesis, which through autocrine signaling initiate an antiviral transcriptional program. Single nucleotide polymorphisms (SNPs) in the IFIH1 gene such as rs1990760, which results in a non-synonymous mutation that changes alanine at position 946 to a threonine, is highly associated with increased risk for T1D. Studies in human PBMCs and mice have demonstrated that the A946T SNP results in an increased sensitivity to viral ligands and subsequently a stronger downstream IFN response. Macrophages have been shown previously to play an important role in T1D initiation, however, the response of β-cells to viral infection is also important. Our central hypothesis is that T1D-associated SNPs result in an exacerbated islet-resident macrophage immune response and β-cell inflammatory response following CVB3 infection which contributes to the initiation of autoimmunity. This will be tested using monocyte- derived macrophages and dendritic cells and induced pluripotent stem cells engineered to become human pancreatic β-cells from healthy donors and patients with T1D that are genotyped for IFIH1 SNPs that contribute to T1D susceptibility and resistance.