A novel genetic mutation reveals the molecular and cellular mechanisms of severe recurrent skin inflammation

项目摘要 先天性免疫缺陷(IEI)是由单基因种系突变引起的遗传性疾病，具有广泛的 临床表现。在此，我们报告两位患坏疽脓皮病(PG)的病人，这是一种非常严重的 罕见且严重的中性粒细胞坏死性皮肤病，无严重的全身性自炎症状。整体 外显子测序(WES)显示每个患者均存在R57C OTULIN错义突变。欧图林 编码一种脱泛素酶，它是唯一一种已知的专门裂解线性泛素链的酶 通过线性泛素链组装复合体(LUBAC)添加到靶蛋白上。余额 在移除和添加泛素之间，对免疫动态平衡和对感染的反应至关重要。 先前报道的生殖系OTULIN突变会影响该蛋白的催化域，并导致严重的 全身性自炎主要由称为OTULIN相关的NF-B信号过度激活所驱动 自体炎症综合征(ORAS)。在这里，我们定义了一种新的单基因疾病，由一种新的基因突变引起 OTULIN的不同结构域，并导致不同的临床表型。我们已经证明了R57C 突变阻止OTULIN与LUBAC组分HOIP结合，但下调NF-B的能力 活性保持不变，这表明OTULIN具有特定于上下文的功能。这些患者的独特表型 这表明OTULIN在皮肤中的一种以前未被认识的功能。这一提议的总体假设 OTULIN在角质形成细胞中的功能不同于其他细胞环境中的功能，而这一新的 突变会导致患者发生坏疽脓皮病。我们将使用计算方法 以及最先进的体外和体外方法来确定翻译后修饰在 调节OTULIN依赖的免疫信号。这一发现增加了人类的新光谱 泛素途径缺陷引起的疾病，提示靶向细胞因子治疗在 维持免疫动态平衡。

PROJECT ABSTRACT Inborn errors of immunity (IEI) are genetic disorders caused by monogenic germline mutations and have broad clinical manifestations. Here, we present two patients affected by pyoderma gangrenosum (PG), an extremely rare and severe neutrophilic necrotic skin disorder, without severe systemic autoinflammatory symptoms. Whole exome sequencing (WES) revealed a homozygous R57C OTULIN missense mutation in each patient. OTULIN encodes a deubiquitinase that is the only known enzyme that specifically cleaves linear ubiquitin chains that have been added to target proteins by the linear ubiquitin chain assembly complex (LUBAC). The balance between removal and addition of ubiquitin is crucial for immune homeostasis and responses to infection. Previously reported germline OTULIN mutations affect this protein’s catalytic domain and cause a severe systemic autoinflammatory largely driven by overactivation of NF-B signaling called OTULIN-related autoinflammatory syndrome (ORAS). Here, we define a new monogenic disease caused by mutations in a different domain of OTULIN and causing a distinct clinical phenotype. We have demonstrated that the R57C mutation prevents OTULIN from binding to the LUBAC component HOIP but the ability to downregulate NF-B activity remains intact suggesting a context-specific function of OTULIN. These patients’ unique phenotype suggests that a previously unrecognized function for OTULIN in the skin. The overall hypothesis of this proposal is that OTULIN’s function in keratinocytes differs from that in other cellular contexts, and this novel mutation leads to development of pyoderma gangrenosum in patients. We will use computational method and cutting-edge in vitro and ex vivo approaches to identify the roles of post-translational modification in regulating OTULIN-dependent immune signaling. This discovery adds to the emerging spectrum of human diseases caused by defects in the ubiquitin pathway and suggests a role for targeted cytokine therapies for maintaining immune homeostasis.