Chen C, Nagy Z, Prak E L, Weigert M
Department of Molecular Biology, Princeton University, New Jersey 08544, USA.
Immunity. 1995 Dec;3(6):747-55. doi: 10.1016/1074-7613(95)90064-0.
We have generated a site-directed transgenic (sd-tg) mouse model in which the JH locus has been replaced with a rearranged VDJ coding for the heavy chain of an anti-DNA antibody. In these mice, B cells expressing the anti-dsDNA specificity are negatively regulated. We observe a novel mechanism for B cell tolerance, receptor editing at the heavy chain locus. In most sd-tg B cells, the inserted anti-DNA VH gene has been replaced by the upstream endogenous VH, or DH, or both genes through recombination with the heptamer embedded at the 3' end of most VH genes. Three types of recombination events have been identified. VH-to-VDJ, DH-to-VDJ, and VH-to-DH-VDJ. Analysis of the junctional sequences revealed features of classical V(D)J rearrangement, namely N sequence addition and nucleotide deletion. A conserved nonamer was found 12 bp upstream of the embedded heptamer. This nonamer may represent a novel recombination signal sequence used for VH editing. The sd-tg model thus provides direct evidence for secondary rearrangement at VH-D-JH. This process may play a role in tolerance by editing autoreactive receptors and may also serve to diversify the VH repertoire.
我们构建了一种位点定向转基因（sd-tg）小鼠模型，其中JH基因座已被编码抗DNA抗体重链的重排VDJ所取代。在这些小鼠中，表达抗双链DNA特异性的B细胞受到负调控。我们观察到一种B细胞耐受性的新机制，即重链基因座处的受体编辑。在大多数sd-tg B细胞中，插入的抗DNA VH基因已通过与大多数VH基因3'端嵌入的七聚体重组，被上游内源性VH或DH或两者基因所取代。已鉴定出三种类型的重组事件。VH-to-VDJ、DH-to-VDJ和VH-to-DH-VDJ。连接序列分析揭示了经典V(D)J重排的特征，即N序列添加和核苷酸缺失。在嵌入的七聚体上游12 bp处发现了一个保守的九聚体。这个九聚体可能代表用于VH编辑的新型重组信号序列。因此，sd-tg模型为VH-D-JH处的二次重排提供了直接证据。这个过程可能通过编辑自身反应性受体在耐受性中发挥作用，也可能有助于使VH库多样化。
