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）是由单基因生殖系突变引起的遗传性疾病，具有广泛的免疫缺陷。 临床表现在这里，我们提出了两个病人的坏疽性脓疡（PG），一个非常 罕见和严重的嗜中性坏死性皮肤病，无严重的全身性自身炎症症状。整个 外显子组测序（WES）揭示了每个患者中的纯合R57 C OTULIN错义突变。奥图林 编码一种去泛素化酶，该酶是唯一已知的特异性切割线性泛素链的酶， 已经通过线性泛素链组装复合物（LUBAC）添加到靶蛋白。余额 泛素的去除和添加之间的关系对于免疫稳态和对感染的反应至关重要。 先前报道的生殖系OTULIN突变影响该蛋白的催化结构域，并导致严重的 全身性自身炎症主要由称为OTULIN相关的NF-κ B B信号过度激活驱动 自身炎症综合征（奥拉斯）。在这里，我们定义了一种新的单基因疾病， 不同的OTULIN结构域并导致不同的临床表型。我们已经证明，R57 C 突变阻止OTULIN与LUBAC组分HOIP结合，但下调NF-κ B B的能力 活性保持完整，表明OTULIN的背景特异性功能。这些病人独特的表型 这表明，一个以前未被认识到的功能OTULIN在皮肤中。这项提议的总体假设是， OTULIN在角质形成细胞中的功能不同于在其他细胞环境中的功能， 突变导致患者发生坏疽性脓毒症。我们将使用计算方法 和尖端的体外和离体方法，以确定翻译后修饰的作用， 调节OTULIN依赖的免疫信号传导。这一发现增加了新兴的人类谱系 疾病引起的泛素途径的缺陷，并提出了针对细胞因子治疗的作用， 维持免疫稳态

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.