Mechanisms of disease in patients with I?B? mutations

 描述(申请人提供)：常染色体显性遗传免疫缺陷外胚层发育不良(AD ED-ID)的特点是头发稀疏，圆锥形牙齿，汗腺数量减少，容易受到严重感染。这是由于IκBα的杂合性突变损害了Ser32和Ser26的磷酸化，并在受体信号转导后随后突变蛋白的降解。这种非降解的突变蛋白在细胞质中积累和隔离NFκB的p50和p65亚基，通过显性的负(DN)效应损害规范的NFκB途径的激活。我们对9例AD ED-ID患者的基因型-表型分析表明，IκBκBα点突变患者的病情严重程度和依赖于TLRB的细胞因子产生障碍明显比N端截短患者严重。我们推测，点突变可能比截断突变更稳定，从而在更高的水平上积累，导致更强的DN效应和更严重的疾病。我们的分析还表明，尽管供者嵌合良好，AD ED-ID患者在造血干细胞移植(HSCT)后的预后很差。我们已经为IκBαS32I突变创造了一个杂合子敲入小鼠，它概括了AD ED-ID患者的表型，S32I小鼠未能发展出接触性超敏反应(CHS)或产生抗体。值得注意的是，突变体完全缺乏次级淋巴器官，包括淋巴结和佩尔氏斑，并且无法形成生发中心(GC)，这两个特征是有缺陷的非典范NFκB信号的典型特征，以前在AD ED-ID患者中没有发现。LTβR诱导的趋化因子和黏附分子通过典型和非典型的NFκB途径均受到抑制，并且非典型的NFκB途径中的P100水平显著降低。IκBα突变体-&gt；RAG2-/-，而不是WT-&gt；IκBα突变体，骨髓嵌合体形成适当的淋巴器官，形成CHS和GCs。这些结果表明，建筑细胞功能缺陷是导致IκBα突变患者移植免疫缺陷和预后不良的原因，纠正这一小生境可能是重建他们免疫功能的关键。我们建议检验这一假设，即IκBα突变蛋白的稳定性与患者细胞中残留的NFκB活性和P100的TH水平成反比，从而决定疾病的严重程度和造血干细胞移植的结局。我们将验证S32I IκBα突变小鼠的间充质干细胞(MSCs)降低P100水平并损害对LTβR结扎反应的假设，并评估WT MSCs在AD ED-ID临床前模型中的潜在治疗策略。

 DESCRIPTION (provided by applicant): Autosomal dominant ectodermal dysplasia with immune deficiency (AD ED-ID) is characterized by sparse hair, conical teeth, reduced number of sweat glands and susceptibility to severe infections. It is due to heterozygous mutations in IκBα that impair Ser32 and Ser26 phosphorylation and subsequent degradation of the mutant protein following receptor signaling. The non-degraded mutant protein accumulates and sequesters the p50 and p65 subunits of NFκB in the cytoplasm, impairing activation of the canonical NFκB pathway through a dominant negative (DN) effect. Our genotype-phenotype analysis of 9 patients with AD ED-ID indicates that disease severity and impairment of NFκB-dependent TLR-driven cytokine production are significantly worse in patients with IκBα point mutations than in those with N-terminal truncations. We hypothesize that the point mutants may be more stable than the truncation mutants, and thereby accumulate at a higher level, resulting in a stronger DN effect and more severe disease. Our analysis also shows that patients with AD ED-ID have a poor outcome after hematopoietic stem cell transplantation (HSCT) despite good donor chimerism. We have created a knock-in mouse heterozygous for the IκBα S32I mutation that recapitulates the phenotype of patients with AD ED-ID, The S32I mouse fails to develop contact hypersensitivity (CHS) or produce antibodies. Strikingly, the mutant completely lacks secondary lymphoid organs including lymph nodes and Peyer's patches, and fails to form germinal centers (GCs), two features typical of defective non-canonical NFκB signaling that were not previously recognized in AD ED-ID patients. LTβR-driven induction of chemokines and adhesion molecules mediated by both canonical and non-canonical NFκB pathways was impaired, and the levels of p100, a component of the non-canonical NFκB pathway, were markedly diminished in the mutant. IκBα mutant->Rag2-/-, but not WT->IκBα mutant, bone marrow chimeras formed proper lymphoid organs, developed CHS and formed GCs. These results suggest that defective architectural cell function underlies the immunodeficiency and poor outcome of HSCT in patients with IκBα mutations, and that correction of this niche may be critical for reconstituting their immune function. We propose to test the hypothesis that the stability of the IκBα mutant protein inversely correlates with the residual NFκB activity and th level of p100 in the patient cells, and thus determines disease severity and the outcome of HSCT. We will test the hypothesis that mesenchymal stem cells (MSCs) from mice with the S32I IκBα mutation have reduced p100 levels and impaired response to LTβR ligation, and to evaluate implantation of WT MSCs as a potential therapeutic strategy in a preclinical model for AD ED-ID.