FUNCTIONAL STUDIES OF IMMUNOGLOBULIN KAPPA ENHANCERS

免疫球蛋白重链（IgH）和轻链（IgL）基因在B细胞分化早期通过可变(V)、多样性(D)和连接(J)基因片段的体细胞组装进行组装。两种IgL链kappa和lambda存在于小鼠体内。似乎IgH和IgL链基因的重排顺序是这样的，IgH重排早于Igkappa，而Igkappa重排早于Iglambda。在Igkappa基因座中发现了两个增强子，它们最初的特征是能够激活b细胞特异性转录。其中一个增强子位于Jkappa和Ckappa之间的内区（iEkappa），另一个位于Ckappa的3′区（3′ekappa）。利用同源重组和loxp - cre介导的缺失，我们和其他人已经证明这两种增强子在数量上是重要的，但不是Igkappa重排所必需的。更重要的是，这两种增强子似乎都参与了Igkappa与Iglambda较早重排的决定。基于这些初步发现，采用相同的方法，我们建议剖析Igkappa重排中iEkappa的功能基序，并测试iEkappa和3'Ekappa在Igkappa重排和表达中的潜在冗余功能。此外，转基因研究表明，这两种K增强子都是Igkappa体细胞超突变的关键。我们将再次采用遗传方法进一步探讨在生理背景下，MiEkappa在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.