DNA Repair Defects in IgA Deficiency

IgA 缺乏症中的 DNA 修复缺陷

• 批准号: 7532736
• 负责人: Reuben S Harris
• 金额: $ 22.43万
• 依托单位: UNIVERSITY OF MINNESOTA
• 依托单位国家: 美国
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-08-15 至 2010-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7532736
• 关键词: Antibodies; Antibody Formation; Antibody Repertoire; Bacteria; Bacterial Infections; Base Excision Repairs; Cells; Common Variable Immunodeficiency; Cytosine; DNA; DNA Repair; DNA Repair Gene; DNA Repair Pathway; DNA Sequence; Deamination; Defect; Diagnosis; Disease; Ensure; European; Event; Excision; Exons; Family; Family Study; Frequencies; Gastrointestinal tract structure; Gene Frequency; Genes; Human; IgA Deficiency; IgE; Immune response; Immunoglobulin A; Immunoglobulin Class Switching; Immunoglobulin Constant Region; Immunoglobulin G; Immunoglobulin M; Immunoglobulin Switch Recombination; Immunologic Deficiency Syndromes; Individual; Laboratories; Mismatch Repair; Mutation; Nonhomologous DNA End Joining; Pathway interactions; Patients; Process; Public Health; Purpose; Range; Serum; Supplementation; System; Technology; Testing; Time; Uracil; Variant; Virus; activation-induced cytidine deaminase; base; cohort; genetic association; member; new technology; pathogen; programs; respiratory

DESCRIPTION (provided by applicant): DNA Repair Defects in IgA Deficiency Immunoglobulin A deficiency (IgAD) is the most common primary immunodeficiency in humans, and it is characterized by the absence of serum IgA and an increased frequency of bacterial infections in the respiratory and gastrointestinal tracts. IgAD may develop over time into a more severe form of antibody deficiency, common variable immunodeficiency (CVID), and the two diseases can even co-exist in different members of the same family suggesting that they represent facets of the same underlying genetic defect(s). In order for IgA to be produced, the expressed heavy chain antibody isotype must be swapped for DNA sequences that encode IgA. This DNA level transaction is called class switch recombination (CSR) and it occurs between two so-called switch region sequences that reside upstream of the respective exons that encode the constant region of the antibody heavy chain. Recent studies have demonstrated that CSR is initiated by AID-catalyzed DNA cytosine deamination events and that the resulting uracil residues are recognized and processed by ubiquitous DNA repair systems such as base excision repair, mismatch repair, non-homologous end-joining and, most recently, single-strand annealing (alternative end-joining pathway). Defects in AID or uracil excision (UNG2) cause an immunodeficiency characterized by high levels of IgM at the expense of other antibody isotypes including IgA. We recently discovered variations in the mismatch repair gene MSH5 that associate with IgAD and CVID. Subsequent preliminary studies in our laboratories have revealed variations in other DNA repair genes that also associate with CVID and/or IgAD. This proposal will build on our prior studies by directly testing the hypothesis that multiple DNA repair defects also contribute to IgAD/CVID. The complete repertoire of known DNA repair genes from a minimum of 400 IgAD/CVID patients will be sequenced by a new technology called massively parallel DNA sequencing or 454 pyrosequencing. After computational analyses, candidate mutations will be validated by re-sequencing and by family studies using the largest IgAD/CVID patient cohort in the world. Key disease-associated mutations will be examined in cell-based systems for defects in DNA repair and in antibody gene diversification program. Overall, we anticipate significantly building upon our prior studies by demonstrating the involvement of several additional DNA repair factors in IgAD/CVID. PUBLIC HEALTH RELEVANCE: Antibodies are a crucial part of our immune response to pathogens such as bacteria and viruses. Recent evidence from many laboratories indicates that ubiquitous DNA repair factors help ensure an effective antibody response by facilitating the DNA level transactions that are required to generate a diverse and strong antibody repertoire. This proposal will determine the complete set of DNA repair gene sequences for more than 400 patients from one of the largest immunodeficiency disease cohorts in the world. We anticipate discovering several new factors that are essential for a robust antibody responses to pathogens.

免疫球蛋白A缺乏症（IgAD）是人类最常见的原发性免疫缺陷，其特征是血清中缺乏IgA，呼吸道和胃肠道细菌感染的频率增加。IgAD可能随着时间的推移发展成一种更严重的抗体缺乏形式，即共同可变免疫缺陷（CVID），这两种疾病甚至可以在同一家庭的不同成员中共存，这表明它们代表了相同的潜在遗传缺陷的各个方面。为了产生IgA，必须将表达的重链抗体同型交换为编码IgA的DNA序列。这种DNA水平的交易被称为类开关重组（CSR），它发生在位于编码抗体重链恒定区域的各自外显子上游的两个所谓的开关区序列之间。最近的研究表明，CSR是由aid催化的DNA胞嘧啶脱氨事件引发的，所产生的尿嘧啶残基被普遍存在的DNA修复系统识别和处理，如碱基切除修复、错配修复、非同源末端连接以及最近的单链退火（替代末端连接途径）。艾滋病或尿嘧啶切除（UNG2）的缺陷导致免疫缺陷，其特征是IgM水平高，而其他抗体同型包括IgA的损失。我们最近发现了与IgAD和CVID相关的错配修复基因MSH5的变异。我们实验室随后的初步研究揭示了与CVID和/或IgAD相关的其他DNA修复基因的变异。这一建议将建立在我们之前的研究基础上，通过直接测试多种DNA修复缺陷也有助于IgAD/CVID的假设。来自至少400名IgAD/CVID患者的完整已知DNA修复基因库将通过一种称为大规模平行DNA测序或454焦磷酸测序的新技术进行测序。计算分析后，候选突变将通过重新测序和使用世界上最大的IgAD/CVID患者队列进行家族研究来验证。关键疾病相关的突变将检查在细胞为基础的系统缺陷的DNA修复和抗体基因多样化程序。总的来说，我们期望通过证明IgAD/CVID中涉及几个额外的DNA修复因子来显著建立我们先前的研究。公共卫生相关性：抗体是我们对病原体（如细菌和病毒）免疫反应的重要组成部分。最近来自许多实验室的证据表明，无处不在的DNA修复因子通过促进DNA水平的交易来帮助确保有效的抗体反应，这些交易需要产生多样化和强大的抗体库。该提案将确定来自世界上最大的免疫缺陷疾病队列之一的400多名患者的完整DNA修复基因序列。我们预计会发现几个新的因素，这些因素对于对病原体的强大抗体反应至关重要。