Choi Y, Greenberg S J, Du T L, Ward P M, Overturf P M, Brecher M L, Ballow M
Department of Neurology, Roswell Park Cancer Institute, Buffalo, NY 14263 USA.
Blood. 1996 Mar 15;87(6):2506-12.
B-cell acute lymphoblastic leukemia (B-ALL), more frequently than any other B-lineage neoplasm, exhibits oligoclonal Ig heavy chain (IgH) gene rearrangement in 15% to 43% of all cases studied. To study the molecular processes that promote multiple IgH rearrangements, a comprehensive sequence analysis of a B-ALL case was performed in which seven clonal IgH gene rearrangements were identified. The genetic profiles suggested that a single leukemic progenitor clone evolved into several subclones through dual processes of variable (VH) to preexisting diversity-joining (DJH) gene segment rearrangement and VH to VH gene replacement. Predominant IgH-V usage and the uniquely rearranged clonotype-specific VHDJH region gene sequences were identified using a novel DNA-based gene amplification strategy. Polymerase chain reaction (PCR) was directed by an IgH-J generic primer and a complement of family-specific IgH-V primers that defined the major B-cell IgH-V gene usage. Clonality of rearranged VHDJH bands was substantiated by high resolution denaturant gel electrophoretic analysis. Sequence patterns of the amplified VHDJH fragments segregated into two groups defined by common DJH sequences. Partial N region homology at the VHD junction as well as shared DJH sequences firmly established VH to VHDJH gene replacement as a mechanism generating clonal evolution in one group. In the second subset, oligoclonality was propagated by independent VH gene rearrangements to a common DJH precursor. The contributions of all clonal Ig-VHDJH repertoires for each group was approximately 50% and reflected a symmetric distribution of leukemic subclones generated by either process. Thus, oligoclonal rearrangements evolved by two independent, yet seemingly contemporaneous molecular genetic mechanisms. All seven clones displayed nonfunctional Ig-VHDJH recombinations. These observations may have relevance to the recombinatorial opportunities available during normal B-cell maturation.
B 细胞急性淋巴细胞白血病（B-ALL）比任何其他 B 系肿瘤更频繁地在所有研究病例的 15%至 43%中表现出寡克隆 Ig 重链（IgH）基因重排。为了研究促进多种 IgH 重排的分子过程，对一例 B-ALL 病例进行了全面的序列分析，其中鉴定出七个克隆性 IgH 基因重排。遗传图谱表明，单个白血病祖细胞克隆通过可变区（VH）与预先存在的多样性连接区（DJH）基因片段重排以及 VH 与 VH 基因置换的双重过程演变成几个亚克隆。使用一种基于 DNA 的新型基因扩增策略鉴定了主要的 IgH-V 使用情况以及独特重排的克隆型特异性 VHDJH 区域基因序列。聚合酶链反应（PCR）由 IgH-J 通用引物和一组定义主要 B 细胞 IgH-V 基因使用情况的家族特异性 IgH-V 引物引导。通过高分辨率变性凝胶电泳分析证实了重排的 VHDJH 条带的克隆性。扩增的 VHDJH 片段的序列模式分为由共同 DJH 序列定义的两组。VHD 连接处的部分 N 区同源性以及共享的 DJH 序列牢固地确立了 VH 到 VHDJH 基因置换是一组中产生克隆进化的机制。在第二个亚组中，寡克隆性通过独立的 VH 基因重排传播到一个共同的 DJH 前体。每组所有克隆性 Ig-VHDJH 库的贡献约为 50%，反映了由任一过程产生的白血病亚克隆的对称分布。因此，寡克隆重排通过两种独立但看似同时发生的分子遗传机制进化。所有七个克隆均显示无功能的 Ig-VHDJH 重组。这些观察结果可能与正常 B 细胞成熟过程中可用的重组机会有关。
