波士顿儿童医院Frederick W. Alt小组近日取得一项新成果。经过不懈努力，他们的研究发现线性RAG扫描介导Igκ可变区谱的编辑。2026年4月15日出版的《自然》杂志发表了这项成果。

在这里，课题组人员描述了阐明生理学上关键的继发性Igk重组机制的研究。原发缺失和倒转的VκJκ1分别连接，删除或置换Cer/Sis，形成一个前B细胞群，在Vκ位点上包含基于VκJ的继发性RCs，并在缺失方向上将大多数未重排的Vκ留在继发性RCs的上游。高通量分析表明，基于VκJκ1的继发性RCs的RAG扫描总体上在原代前B细胞群的Vκ位点上呈线性延伸。相应的，对诱导多能干细胞（iPS）生成的小鼠模型或具有生理VκJκ重排的细胞系的研究进一步表明，通过线性RAG扫描，基于Jκ2-5的继发性RCs在缺失方向上捕获了缺失的和原本倒置的Vκ。强的Vκ-RSs有助于将次要重排（包括潜在的编辑重排）限制在给定次要RC上游的Vκs上，并在较低水平上支持基于线性扫描的逆Vκ-到Jκ重排。他们的研究结果表明，Cer/Sis缺失和/或位移是一个发育开关，将基于双环的差异初级Igk重排机制转变为基于单环的线性扫描次级重排机制。

研究人员表示，前体（前）B细胞中V(D)J重组介导的Igκ轻链可变区外显子组装涉及重组激活基因（RAG）内切酶介导的配对Vκ和Jκ基因片段之间的切割和连接以及侧翼的RAG靶向重组信号序列（RSSs）。3.1兆碱基的Igk包含4个碱基（碱基1、2、4、5）和100兆碱基的碱基（碱基1、2、4、5）。Vκ-到Jκ的连接是有序的，首先发生初级的Vκ-对Jκ1的重排，然后上游的Vκ的次级重排，通过与Jκ2-5的连接取代初级的VκJκ1s。环挤压将缺失导向和逆转录导向的局域范围内的Vκs通过基于Cer/Sis ctcf结合元件的分化平台，在初级重组中心（primary recombination centre， RC）向Jκ 1结合的RAG进行短程分化呈递。为了实现差异介导的Vκ-to-Jκ1连接，Igk进化出强大的Vκ相关和Jκ相关的RSSs3。继发性Igk重排取代无功能或自身反应性的原发性VκJκ1重排，通过受体编辑扩大Igκ库并介导中枢耐受。

附：英文原文

Title: Linear RAG scanning mediates editing of Igκ variable region repertoires

Author: Li, Xiang, Hu, Hongli, Zhang, Yiwen, Zhu, Tammie, Guan, Ying, Xu, Kai, Lin, Xin, Hebert, Camille, Batra, Himanshu, Zhou, Jenny, Ba, Zhaoqing, Wesemann, Duane R., Ye, Adam Yongxin, Alt, Frederick W.

Issue&Volume: 2026-04-15

Abstract: V(D)J recombination-mediated Igκ light chain variable region exon assembly in precursor (pre)-B cells involves recombination activating gene (RAG) endonuclease-orchestrated cleavage between and joining of paired Vκ and Jκ gene segments and flanking RAG-targeting recombination signal sequences (RSSs)1,2,3. The 3.1-megabase Igk contains 4 Jκs (Jκ1, 2, 4, 5) and 100-plus Vκs in clusters oriented for deletional or inversional joining2. Vκ-to-Jκ joining is ordered, with primary Vκ-to-Jκ1 rearrangements occurring first, followed by secondary rearrangements of upstream Vκs that replace primary VκJκ1s by joining to Jκ2-5 (refs. 4,5). Loop extrusion moves deletional-oriented and inversional-oriented, locus-wide Vκs past the Cer/Sis CTCF-binding element-based diffusion platform for short-range diffusional presentation to Jκ1-bound RAG in the primary recombination centre (RC). To achieve diffusion-mediated Vκ-to-Jκ1 joining, Igk evolved powerful Vκ-associated and Jκ-associated RSSs3. Secondary Igk rearrangements replace non-functional or autoreactive primary VκJκ1 rearrangements, expanding the Igκ repertoire and mediating central tolerance by means of receptor editing4,6,7,8,9,10,11. Here we describe studies that elucidate the physiologically critical secondary Igk recombination mechanism. Primary deletional and inversional VκJκ1 joins, respectively, delete or displace Cer/Sis, creating a pre-B cell population that harbours secondary VκJκ1-based RCs across the Vκ locus and leaves most unrearranged Vκs immediately upstream of secondary RCs in deletional orientation. High-throughput assays demonstrated that RAG scanning from secondary VκJκ1-based RCs, collectively, extends linearly across the Vκ locus in primary pre-B cell populations. Correspondingly, studies of induced pluripotent stem (iPS) cell-generated mouse models or cell lines with physiological VκJκ-rearrangements further revealed that deletional and, originally, inversional Vκs are mostly captured by Jκ2-5-based secondary RCs in deletional orientation by means of linear RAG scanning. Strong Vκ-RSSs contribute to restricting secondary rearrangements, including potential editing rearrangements, to Vκs immediately upstream of a given secondary RC and support, at a lower level, linear scanning-based inversional Vκ-to-Jκ rearrangements. Our findings implicate Cer/Sis deletion and/or displacement as a developmental switch that converts the two-loop-based diffusional primary Igk rearrangement mechanism into a one-loop-based linear scanning secondary rearrangement mechanism.

DOI: 10.1038/s41586-026-10362-5

Source: https://www.nature.com/articles/s41586-026-10362-5