Diffuse large B-cell lymphoma (DLBCL) is the most common lymphoma. A major mutagenic process in DLBCL is aberrant somatic hypermutation (aSHM) by activation-induced cytidine deaminase (AID), which occurs preferentially at RCH/TW sequence motifs proximal to transcription start sites. Splice sequences are highly conserved, rich in RCH/TW motifs, and recurrently mutated in DLBCL. Therefore, we hypothesized that aSHM may cause recurrent splicing mutations in DLBCL. In a meta-cohort of > 1,800 DLBCLs, we found that 77.5% of splicing mutations in 29 recurrently mutated genes followed aSHM patterns. In addition, in whole-genome sequencing (WGS) data from 153 DLBCLs, proximal mutations in splice sequences, especially in donors, were significantly enriched in RCH/TW motifs (p < 0.01). We validated this enrichment in two additional DLBCL cohorts (N > 2,000; p < 0.0001) and confirmed its absence in 12 cancer types without aSHM (N > 6,300). Comparing sequencing data from mouse models with and without AID activity showed that the splice donor sequences were the top genomic feature enriched in AID-induced mutations (p < 0.0001). Finally, we observed that most AID-related splice site mutations are clonal within a sample, indicating that aSHM may cause early loss-of-function events in lymphomagenesis. Overall, these findings support that AID causes an overrepresentation of clonal splicing mutations in DLBCL.

中文翻译：

---

激活诱导的胞苷脱氨酶导致弥漫性大 B 细胞淋巴瘤反复剪接突变

弥漫性大 B 细胞淋巴瘤 (DLBCL) 是最常见的淋巴瘤。DLBCL 中的一个主要诱变过程是由激活诱导的胞苷脱氨酶 (AID) 引起的异常体细胞超突变 (aSHM)，该突变优先发生在靠近转录起始位点的 RCH/TW 序列基序上。剪接序列高度保守，富含 RCH/TW 基序，并且在 DLBCL 中反复突变。因此，我们推测aSHM可能导致DLBCL中反复出现剪接突变。在超过 1,800 个 DLBCL 的元队列中，我们发现 29 个反复突变基因中 77.5% 的剪接突变遵循 aSHM 模式。此外，在 153 个 DLBCL 的全基因组测序 (WGS) 数据中，剪接序列的近端突变（尤其是供体中的）在 RCH/TW 基序中显着富集 (p < 0.01)。我们在另外两个 DLBCL 队列中验证了这种富集（N > 2,000；p < 0.0001），并证实在没有 aSHM 的 12 种癌症类型中不存在这种富集（N > 6,300）。比较具有和不具有 AID 活性的小鼠模型的测序数据表明，剪​​接供体序列是富含 AID 诱导突变的首要基因组特征 (p < 0.0001)。最后，我们观察到大多数 AID 相关剪接位点突变在样品中是克隆的，表明 aSHM 可能导致淋巴瘤发生中的早期功能丧失事件。总体而言，这些发现支持 AID 导致 DLBCL 中克隆剪接突变的过度表达。