Concordance for type 1 diabetes (T1D) is far from 100% in monozygotic twins and in inbred nonobese diabetic (NOD) mice, despite genetic identity and shared environment during incidence peak years. This points to stochastic determinants, such as postzygotic mutations (PZMs) in the expanding antigen-specific autoreactive T cell lineages, by analogy to their role in the expanding tumor lineage in cancer. Using comparative genomic hybridization of DNA from pancreatic lymph-node memory CD4+ T cells of 25 diabetic NOD mice, we found lymphocyte-exclusive mosaic somatic copy-number aberrations (CNAs) with highly nonrandom independent involvement of the same gene(s) across different mice, some with an autoimmunity association (e.g., Ilf3 and Dgka). We confirmed genes of interest using the gold standard approach for CNA quantification, multiplex ligation-dependent probe amplification (MLPA), as an independent method. As controls, we examined lymphocytes expanded during normal host defense (17 NOD and BALB/c mice infected with Leishmania major parasite). Here, CNAs found were fewer and significantly smaller compared to those in autoreactive cells (P = 0.0019). We determined a low T cell clonality for our samples suggesting a prethymic formation of these CNAs. In this study, we describe a novel, unexplored phenomenon of a potential causal contribution of PZMs in autoreactive T cells in T1D pathogenesis. We expect that exploration of point mutations and studies in human T cells will enable the further delineation of driver genes to target for functional studies. Our findings challenge the classical notions of autoimmunity and open conceptual avenues toward individualized prevention and therapeutics.

中文翻译：

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糖尿病NOD小鼠自身反应性T淋巴细胞的克隆拷贝数镶嵌术。

尽管单基因双生子和近亲非肥胖糖尿病（NOD）小鼠的1型糖尿病（T1D）一致性远非100％，尽管在发病高峰期具有遗传同一性和共有的环境。这类似于它们在癌症中扩展肿瘤谱系中的作用，从而指出了随机决定因素，例如扩展的抗原特异性自身反应性T细胞谱系中的合子后突变（PZM）。使用来自25个糖尿病NOD小鼠的胰腺淋巴结记忆CD4 + T细胞的DNA的比较基因组杂交，我们发现淋巴细胞排斥的马赛克体细胞拷贝数畸变（CNA）具有相同的基因在不同小鼠之间的高度非随机独立参与，有些与自身免疫相关（例如Ilf3和Dgka）。我们使用黄金标准方法对CNA进行了量化，从而确定了感兴趣的基因，多重连接依赖探针扩增（MLPA）作为独立方法。作为对照，我们检查了在正常宿主防御过程中扩增的淋巴细胞（感染了利什曼原虫主要寄生虫的17只NOD和BALB / c小鼠）。在这里，与自反应性细胞相比，发现的CNA更少且明显更小（P = 0.0019）。我们确定了样本的低T细胞克隆性，表明这些CNA的胸腺形成。在这项研究中，我们描述了T1D发病机制中PZMs在自身反应性T细胞中的潜在因果贡献的新的，尚未探索的现象。我们期望对人类T细胞中的点突变和研究的探索将使驱动基因的进一步描绘成为功能研究的目标。