The Regulation of B Lymphocyte Development

描述（由申请方提供）：B细胞发育产生大量多样的单特异性和自身耐受性B细胞库，表达表面免疫球蛋白（IG）作为其抗原受体的识别组分。IG多样性依赖于被称为V（D）J重组的严格调控的新型位点特异性DNA重组反应，其从其组分基因片段组装IG重链和轻链基因的可变外显子。一对淋巴特异性蛋白质RAG 1和RAG 2彼此形成复合物，识别成对的重排基因片段并帮助催化它们的连接。这一过程在淋巴发育过程中受到以下方面的调节：谱系（IG基因在B细胞中完全重排，但在T细胞中不重排）、谱系内的顺序（重链在轻链之前重排）和等位基因的使用（单个细胞在其表面上仅表达一种功能性IG分子，这种现象称为等位基因排斥）。先前的工作已经表明，重组酶的靶向取决于染色质结构内基因区段的可接近性，并且未重排基因区段的转录与它们对重组酶的可接近性相关。这一关于B细胞发育调控的长期研究计划的竞争性更新旨在通过追求四个特定目标来理解在原代B细胞库产生期间调控V（D）J重组的机制。1)鉴定RAG 1和RAG 2基因转录调控所需的顺式作用DNA序列和反式作用因子：2）确定IG κ基因座如何被激活以在前B细胞中转录和重排，使得只有一个等位基因功能性重排; 3）确定转录因子NF-κ B在B细胞库的受体编辑和正选择的调节中起什么作用（如果有的话）;和4）检验关于IgHC V至DJ重排的谱系特异性和等位基因排除的机制的假设。这些研究是有意义的，因为缺陷的V（D）J重组可导致严重的免疫缺陷，因为靶向重组酶的错误与基因组不稳定性、染色体易位和恶性肿瘤相关，并且因为重组酶的适当调节是避免自身免疫性疾病所必需的。

DESCRIPTION (provided by applicant): B cell development generates a large and diverse repertoire of mono-specific and self-tolerant B cells expressing surface immunoglobulin (Ig) as the recognition component of their antigen receptor. Ig diversity depends upon a tightly regulated novel site-specific DNA recombination reaction known as V(D)J recombination which assembles the variable exons of the Ig heavy-chain and light-chain genes from their component gene-segments. A pair of lymphoid-specific proteins, RAG1 and RAG2, form a complex with one another that recognizes pairs of rearranging gene segments and helps catalyze their joining. This process is regulated during lymphoid development with respect to lineage (Ig genes fully rearrange in B but not T cells), order within the lineage (heavy-chain rearranges before light-chain), and the use of alleles (an individual cell expresses only one functional Ig molecule on its surface, a phenomenon known as allelic exclusion). Previous work has shown that targeting of the recombinase depends upon the accessibility of gene- segments within chromatin structure and that transcription of unrearranged gene segments correlates with their accessibility to the recombinase. This competing renewal of a long-standing program of research on the regulation of B cell development aims to understand the mechanisms which regulate V(D)J recombination during generation of the primary B cell repertoire through the pursuit of four specific aims. 1) To identify the cis-acting DNA sequences and trans-acting factors which are required for the transcriptional regulation of the RAG1 and RAG2 genes; 2) To determine how the Ig kappa locus is activated for transcription and rearrangement in pre-B cells in such a fashion that only one allele is functionally rearranged; 3) To determine what role if any the transcription factor NF-kB plays in the regulation of receptor editing and positive selection of the B cell repertoire; and 4) to test hypotheses regarding the mechanisms of lineage specificity and allelic exclusion of IgHC V-to-DJ rearrangement. These studies are significant because defective V(D)J recombination can lead to profound immunodeficiency, because mistakes in targeting the recombinase are associated with genomic instability, chromosomal translocations, and malignancy, and because appropriate regulation of the recombinase is necessary to avoid autoimmune disease.