Immunoglobulin Constant Region Switch and Hypermutation in the Nurse Shark

护士鲨的免疫球蛋白恒定区转换和超突变

• 批准号: 8008955
• 负责人: ELLEN HSU
• 金额: $ 11.02万
• 依托单位: SUNY DOWNSTATE MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-01-28 至 2011-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8008955
• 关键词: Alleles; Antibody Diversity; Antigen Receptors; Autoimmunity; Award; B-Lymphocytes; Biological Models; Cell surface; Cells; Complementary DNA; DNA; DNA Sequence Rearrangement; Data; Disease; Ensure; Enzymes; Event; Exclusion; Feedback; Frequencies; Gene Expression; Gene Structure; Gene Targeting; Genes; Genetic; Genomics; Hand; Immune system; Immunization; Immunoglobulin Class Switching; Immunoglobulin Constant Region; Immunoglobulin Genes; Immunoglobulin M; Immunoglobulin Somatic Hypermutation; Immunoglobulin Switch Recombination; Immunoglobulins; J segment gene; Jaw; Lesion; Light; Longitudinal Studies; Lymphocyte; Malignant lymphoid neoplasm; Mammals; Mitosis; Mutate; Nature; Nurses; Nursing Models; Pathogenesis; Point Mutation; Process; Regulatory Pathway; Research; Resolution; Secure; Shark; Staging; Stretching; System; Time; V(D)J Recombination; Vertebrates; activation-induced cytidine deaminase; base; insight; mutant; novel; pathogen; public health relevance; receptor; recombinase; repaired; research study

DESCRIPTION (provided by applicant): The adaptive immune system is founded on lymphocytes expressing a vast array of antigen receptors that provide specific recognition in responding to pathogen. Receptor diversity is generated by V(D)J rearrangement and, in immunoglobulin (Ig) genes, post-rearrangement somatic hypermutation. In higher vertebrates mechanisms involving not only hierarchical activation of the 3 Ig loci but also feedback by a successful rearrangement are thought to restrict expression to one allele and one isotype (allelic and isotype exclusion). This process, which ensures primarily one receptor species per cell, is not well understood. Elucidating shared and divergent regulatory pathways in mammals and in sharks, representatives of the earliest vertebrates with a RAG recombinase-based immune system, will allow us to gain insight into the underlying principles upon which adaptive immune systems are constructed. Preliminary data suggest that shark B cells expressing one light (L) chain type at the cell surface also transcribe other L chain types. However, it is not clear how the more than 70 L chain miniloci in nurse shark are regulated. Specific Aim 1 is to examine L chain expression in single shark B cells and determine whether there is clonal expression of the antigen receptor. Some heavy (H) chain cDNA sequences contain V(D)J in combination with C regions different from what is anticipated from the established genomic organization. This genetic exchange occurs somatically and between distantly located IgH genes; it resembles the H chain switch recombination that exists in mammals. Specific Aim 2 is to determine the linkage relationship among the 15 IgH genes and investigate the mechanistic basis for the IgH chain switching process in sharks. Since the switching occurs at the same time as somatic hypermutation, it is hypothesized that both are initiated activation- induced cytidine deaminase. Hypermutation in shark Ig uniquely includes tandem changes of 2-5 bp stretches and sometimes non-templated insertions. To understand how these changes are generated, we will in Specific Aim 3 isolate activated B cells in G2/M phase of the cell cycle, looking for those carrying both mutated and parental V(D)J sequence. The proposed research is part of long-term studies on Ig gene expression in early vertebrates. Understanding the nature of B lymphocyte diversification mechanisms involving DNA breakage and repair will provide insight into the pathogenesis of disease states that include autoimmunity and lymphoid malignancies predisposed by aberrant translocations. PUBLIC HEALTH RELEVANCE: Our shark model system carries about 85 immunoglobulin genes that are targeted by enzymes introducing nicks or lesions in the course of generating antibody diversity. We have observed genetic exchange taking place between the distantly located loci. Studying these phenomena will help determine parameters for genetic exchange between non-allelic genes and give insight into the origins of somatic translocation events leading to disease states.

描述（由申请人提供）：适应性免疫系统建立在表达大量抗原受体的淋巴细胞上，这些抗原受体在响应病原体时提供特异性识别。受体多样性由V（D）J重排产生，并且在免疫球蛋白（IG）基因中，由重排后体细胞超突变产生。在高等脊椎动物中，不仅涉及3个IG基因座的分级激活，而且还涉及通过成功重排的反馈的机制被认为将表达限制于一个等位基因和一个同种型（等位基因和同种型排除）。这一过程主要确保每个细胞有一种受体，但目前还不清楚。阐明哺乳动物和鲨鱼中的共同和不同的调控途径，最早的脊椎动物与RAG重组酶为基础的免疫系统的代表，将使我们能够深入了解适应性免疫系统构建的基本原则。初步数据表明，鲨鱼B细胞在细胞表面表达一种轻（L）链类型，也转录其他L链类型。然而，目前尚不清楚护士鲨中超过70 L的链微生物是如何调节的。具体目的1是检测单个鲨鱼B细胞中L链的表达，并确定是否存在抗原受体的克隆表达。一些重（H）链cDNA序列含有V（D）J与C区的组合，与从已建立的基因组组织中预期的不同。这种遗传交换发生在体细胞和遥远的IgH基因之间;它类似于哺乳动物中存在的H链开关重组。具体目标2是确定15个IgH基因之间的连锁关系，并探讨鲨鱼IgH链转换过程的机制基础。由于转换与体细胞超突变同时发生，因此假设两者都是激活诱导的胞苷脱氨酶。鲨鱼IG中的超突变独特地包括2-5 bp延伸的串联变化，有时包括非模板插入。为了理解这些变化是如何产生的，我们将在特异性目标3中分离细胞周期G2/M期的活化B细胞，寻找那些携带突变和亲本V（D）J序列的细胞。这项研究是早期脊椎动物IG基因表达长期研究的一部分。理解涉及DNA断裂和修复的B淋巴细胞多样化机制的性质将提供对疾病状态的发病机制的深入了解，所述疾病状态包括由异常易位诱发的自身免疫和淋巴恶性肿瘤。公共卫生关系：我们的鲨鱼模型系统携带大约85个免疫球蛋白基因，这些基因在产生抗体多样性的过程中被引入切口或病变的酶靶向。我们观察到基因交换发生在相距遥远的基因座之间。研究这些现象将有助于确定非等位基因之间的遗传交换参数，并深入了解导致疾病状态的体细胞易位事件的起源。