Does post-transcriptional control of NLRP3 inflammasome activity impact development of type 1 diabetes?

人类基因组包含大量的顺式和反式作用的调控元件，其在从基因转录到翻译的过程中的不同点调节基因活性。在全基因组关联研究（GWAS）中，基因组的非编码或调控区的改变与自身免疫性1型糖尿病（T1 D）相关，表明基因或基因产物表达的变化可能在功能性免疫失调中起重要作用。我们已经在NLRP 3的3 ′-UTR（非翻译区）中鉴定了多个转录后调控元件，NLRP 3是代谢功能障碍的胞质先天免疫传感器，其影响NLRP 3 mRNA稳定性并与T1 D风险相关。NLRP 3激活导致称为炎性小体的大寡聚信号传导复合物的组装，其促进称为焦亡的炎性细胞死亡形式和生物活性IL-1β（一种与T1 D的病理生理学有关的促炎细胞因子）的产生。在NOD（非肥胖糖尿病）小鼠模型中，NLRP 3缺陷通过IL-1β的产生受损和致病性T细胞向胰岛的迁移减少来防止T1 D的发展，这表明NLRP 3炎性体在T1 D发病机制中起关键作用。虽然这一系列相关事件已得到很好的描述，但对控制NLRP 3表达并设定炎性小体激活阈值和与T1 D发展相关的病理事件的转录后机制知之甚少。我们的遗传数据证明，在人类NLRP 3基因的3 ′-UTR中的单核苷酸多态性在功能上增加NLRP 3 mRNA与T1 D风险显著相关，这表明NLRP 3的增加可能在疾病发展中起作用。我们已经发现NLRP 3基因也有两个多聚腺苷酸化位点，其编码稳定的短3 ′-UTR或不太稳定的长3 ′-UTR。较长的3 ′-UTR含有几个顺式作用的调控基序，如富含AU的元件、miRNA结合位点和翻译元件的γ干扰素抑制剂，已知其抑制蛋白质表达。基于这些数据，我们假设优先使用短3 '-UTR而不是长3'-UTR增加了NLRP 3的基因剂量，从而使细胞对NLRP 3激活剂敏感并降低T1 D中NLRP 3炎性小体激活的阈值。在这项授权中，我们将产生在NOD背景下携带NLRP 3的短与长3 '-UTR变体的小鼠，目的是通过交替使用3'-UTR来剖析NLRP 3的基因剂量对体内T1 D的发展和进展的影响。我们的研究将产生基础小鼠模型来研究转录后调控在T1 D发展中的作用，并将对理解遗传变异引起的表达变化如何影响复杂自身免疫性疾病（如T1 D）的发展产生更广泛的影响。

The human genome contains a large number of cis- and trans-acting regulatory elements that modulate gene activity at different points in the progression from gene transcription to translation. Alterations in non-coding or regulatory regions of the genome are linked to autoimmune type 1 diabetes (T1D) in Genome-wide association studies (GWAS), suggesting that changes in gene or gene product expression might play an important role in functional immune dysregulation. We have identified multiple post-transcriptional regulatory elements in the 3Ꞌ-UTR (untranslated region) of NLRP3, a cytosolic innate immune sensor of metabolic dysfunction, that impact NLRP3 mRNA stability and are associated with T1D risk. NLRP3 activation results in assembly of a large oligomeric signaling complex called the inflammasome that promotes a form of inflammatory cell death called pyroptosis and production of bioactive IL-1β, a pro-inflammatory cytokine implicated in the pathophysiology of T1D. In the NOD (non-obese diabetic) mouse model, NLRP3 deficiency protects from development of T1D through impaired production of IL-1β and reduced migration of pathogenic T cells to the pancreatic islets, suggesting a critical role for the NLRP3 inflammasome in T1D pathogenesis. While this set of linked events is well described, little is known about the post-transcriptional mechanisms that control the expression NLRP3 and set the threshold for inflammasome activation and the pathological events associated with development of T1D. Our genetic data document that a single nucleotide polymorphism in the 3Ꞌ-UTR of the human NLRP3 gene that functionally increases NLRP3 mRNA is significantly associated with T1D risk suggesting that an increase in NLRP3 may play a role in disease development. We have found that the NLRP3 gene also has two polyadenylation sites, which either encode for a stable short 3Ꞌ-UTR or a less stable longer 3Ꞌ-UTR. The longer 3Ꞌ-UTR harbors several cis acting regulatory motifs, such as AU-rich elements, miRNA binding sites and gamma interferon inhibitor of translation elements, which are known to suppress protein expression. Based on these data we hypothesize that preferential usage of the short 3'-UTR as opposed to the long 3'-UTR increases the gene dosage of NLRP3 thereby sensitizing cells to NLRP3 activators and lowering the threshold for NLRP3 inflammasome activation in T1D. In this grant we will generate mice carrying the short vs. long 3'-UTR variants of NLRP3 on the NOD background with the goal of dissecting the impact of gene dosage of NLRP3 via alternate 3Ꞌ-UTR usage on the development and progression of T1D in vivo. Our study will generate foundational mouse models to study the role of post-transcriptional regulation in development of T1D and will have broader implications for understanding how expression changes caused by genetic variation impact the development of complex autoimmune diseases like T1D.