FUNCTIONAL STUDIES OF IMMUNOGLOBULIN KAPPA ENHANCERS

免疫球蛋白重链（IgH）和轻链（IgL）基因在B细胞分化的早期阶段通过可变（V）、多样性（D）和连接（J）基因区段的体细胞组装来组装。 两个IgL链，κ和λ，存在于小鼠中。 似乎IgH和IgL链基因以顺序方式重排，使得IgH重排早于Igkappa，而Igkappa重排早于Iglambda。 在Igkappa基因座中已经鉴定出两种增强子，其最初特征在于其激活B细胞特异性转录的能力。 其中一个增强子位于Jkappa和Ckappa之间的内含子区（iEkappa），另一个位于Ckappa的3'端（3' Ekappa）。 采用同源重组和LoxP-Cre介导的缺失，我们和其他人已经表明，这两个增强子是定量重要的，但不是必需的Igkappa重排。 更重要的是，这两种增强子似乎都参与了Igkappa与Iglambda的早期重排的确定。 基于这些初步的发现，并采用相同的方法，我们建议解剖的功能基序内的iEkappa的Igkappa重排，并测试潜在的冗余功能的iEkappa和3 'Ekappa的Igkappa重排和表达。此外，转基因研究表明，这两个K增强子是至关重要的体细胞超突变的Igkappa。 我们将再次采用遗传学方法进一步探索MiEkappa在生理背景下Igkappa体细胞超突变中的功能。

Immunoglobulin heavy (IgH) and light chain (IgL) genes are assembled through the somatic assembly of the variable (V), diversity (D) and joining (J) gene segments during the early stage of B cell differentiation. Two IgL chains, kappa and lambda, are present in mice. It appears that IgH and IgL chain genes are rearranged in a sequential manner such that IgH rearranges earlier than Igkappa while Igkappa rearranges earlier than Iglambda. Two enhancers, originally characterized by their ability to activate B-cell specific transcription, have been identified in the Igkappa locus. One of the enhancer is located in the intronal region between Jkappa and Ckappa (iEkappa) and the other located 3' of Ckappa (3'Ekappa). Employing homologous recombination and LoxP-Cre-mediated deletion, we and others have shown that both enhancers are quantitatively important but not essential for the Igkappa rearrangement. More importantly, both enhancers appear to be involved in the determination of the earlier rearrangement of Igkappa versus Iglambda. Based on these initial findings and employing the same methodology, we propose to dissect the functional motifs within iEkappa in the Igkappa rearrangement and to test the potential redundant functions of iEkappa and 3'Ekappa in the Igkappa rearrangement and expression. In addition, transgenic studies have suggested that both K enhancers are critical for somatic hypermutation of Igkappa. We will again employ genetic approaches to further explore the functions of MiEkappa in somatic hypermutations of Igkappa in a physiological context.