VH replacement rescues progenitor B cells with two nonproductive VDJ alleles
VH replacement rescues progenitor B cells with two nonproductive VDJ alleles
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DOI：
10.4049/jimmunol.177.10.7007
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发表时间：
2006-11-15
影响因子：
4.4
通讯作者：
Jack, Hans-Martin
中科院分区：
文献类型：
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作者：
Lutz, Johannes;Muller, Werner;Jack, Hans-Martin
不准确的 VDJ 重排会产生大量带有两个非生产性 IgH 等位基因的祖 (pro)-B 细胞。此类细胞缺乏由表面 IgM 重链（mu H 链）表达介导的必需生存信号，通常会被消除。然而，在生产性 mu H 链转基因小鼠中，已经描述了上游 V. 基因片段二次重排为组装的 VDJ 外显子，这一过程称为 V-H 替换。如果 V-H 替换独立于 mu H 链信号，它还可以修改非生产性 VDJ 外显子，从而挽救两个等位基因重排失败的亲 B 细胞。为了检验这一假设，我们用非生产性 VDJ 外显子同源替换了小鼠的 J(H) 簇。令人惊讶的是，IgH(VDJ-/VDJ-) 小鼠中的 B 细胞发育仅受到轻微损害，并且产生了大量 IgM 阳性 B 细胞。 DNA测序证实，来自mu H链阳性B淋巴细胞的所有VDJ序列都是通过V-H替换以RAG依赖性方式产生的。我们的转基因小鼠的另一个独特特征是存在具有异常长的 CDR3-H 区域的 IgH 链。这样的 IgH 链是有功能的，并且只是适度地反选择，反对 CDR3-H 区域的严格长度限制。总之，V-H 替换可以在没有 mu H 链信号的情况下发生，并为具有两个非生产性 IgH 等位基因的 pro-B 细胞提供潜在的救援机制。
Inaccurate VDJ rearrangements generate a large number of progenitor (pro)-B cells with two nonproductive IgH alleles. Such cells lack essential survival signals mediated by surface IgM heavy chain (mu H chain) expression and are normally eliminated. However, secondary rearrangements of upstream V. gene segments into assembled VDJ exons have been described in mice transgenic for productive mu H chains, a process known as V-H replacement. If V-H replacement was independent of mu H chain signals, it could also modify nonproductive VDJ exons and thus rescue pro-B cells with unsuccessful rearrangements on both alleles. To test this hypothesis, we homologously replaced the J(H) cluster of a mouse with a nonproductive VDJ exon. Surprisingly, B cell development in IgH(VDJ-/VDJ-) mice was only slightly impaired and significant numbers of IgM-positive B cells were produced. DNA sequencing confirmed that all VDJ sequences from mu H chain-positive B lymphoid cells were generated by V-H replacement in a RAG-dependent manner. Another unique feature of our transgenic mice was the presence of IgH chains with unusually long CDR3-H regions. Such IgH chains were functional and only modestly counter-selected, arguing against a strict length constraint for CDR3-H regions. In conclusion, V-H replacement can occur in the absence of a mu H chain signal and provides a potential rescue mechanism for pro-B cells with two nonproductive IgH alleles.