MCM8 突变致I型干扰素负调控功能失活促进川崎病发病风险的作用及机制研究

Kawasaki disease (KD) is a serious pediatric systemic vasculitis that seriously affects the health of infants and young children. Viral infection is a major cause of KD with the mechanism unrevealed. Our preliminary results showed that the type I interferon in KD patients was significantly higher than control group, and it continued to be expressed regardless the clearance of etiology, suggesting the dysfunction of type I interferon pathway. Genome-wide sequencing revealed that MCM8 S365N mutation was significantly enriched in KD children compared to the control group. Further experiment showed that overexpression of MCM8 inhibit the production of type I interferon, while the S365N mutant showed loss-of-function phenotype. Does MCM8 S365N mutation and dysfunction of type I interferon increase susceptibility to infection-induced KD in children? In combination with clinical samples, this project intend to demonstrate the function and mechanism of MCM8 S365N on type I interferon pathway. And we will determine whether MCM8 S365N mutation increases the susceptibility to infection-induced KD through animal model. In this study, we will describe the mechanism of negative regulation of type I interferon by MCM8, and provide new insight for prevention and treatment of KD.

川崎病（KD）是严重影响婴幼儿健康的全身性血管炎，常伴血栓、冠状动脉瘤等严重并发症，预防和治疗棘手。病毒感染是KD发病的重要诱发因素，但机制不详。预实验结果显示KD患者血浆中I型干扰素水平较对照显著升高，且在感染清除后持续表达，提示I型干扰素通路负调控缺陷；全外显子测序发现MCM8 S365N 突变在KD儿童中较千人对照显著富集。功能实验进一步证实过表达MCM8抑制RIG-I介导的I型干扰素表达，S365N突变体则缺失该负调控功能。MCM8 S365N突变致I型干扰素负调控失活是否增加儿童对感染诱发KD的易感性？本项目拟结合临床标本从分子水平阐述MCM8 S365N功能突变对I型干扰素信号途径的影响及具体机制，并通过动物模型确立MCM8 S365N突变是否增加感染诱发KD的易感性。本研究首次阐述MCM8负调控I型干扰素的机制，将为预防和治疗KD提供新的思路。

川崎病（KD）是严重影响婴幼儿健康的全身性血管炎，常伴血栓、冠状动脉瘤等严重并发症，预防和治疗棘手。我们研究发现血管炎和I型干扰素的异常升高有密切联系，并详细阐述MCM8负调控I型干扰素的机制，为预防和治疗KD提供新的思路。感染等多种外界因素均可引起I型干扰素的激活，内在因素则主要包括基因组DNA或线粒体DNA的损伤。为了探索机体基因与内在因素对血管炎的调控，我们关注到迷你染色质维稳基因MCM家族成员MCM8。MCM8调控DNA复制及DNA损伤修复，然而其是否影响I型干扰素和血管炎仍待探索。我们构建MCM8敲除小鼠和敲除细胞，发现MCM8敲除能够促进I型干扰素的产生，并促进血管炎的发生发展，围绕MCM8对I型干扰素和血管炎的影响，我们展开了系统的研究，我们发现我们发现MCM8缺失的巨噬细胞在血管炎的发生发展中发挥重要作用。在机制研究中，我们发现在外界刺激下，细胞产生NO，促进TRIM21介导的MCM8的泛素化出核 ，出核后的MCM8作为线粒体自噬的受体，通过清除损伤线粒体抑制胞浆中线粒体DNA的积累，限制了cGAS-STING介导的I型干扰素的激活，抑制了血管炎的发生发展。更重要的是，我们发现东亚人群在LIR motif存在高频突变A276P通过影响线粒体自噬影响川崎病的发生发展，这为川崎病乃至广泛血管炎的诊断和治疗提供了新的靶点和思路。