ABSTRACT

Acute myeloid leukaemia (AML) is a heterogeneous myeloid malignancy characterized by recurrent clonal events, including mutations in epigenetically relevant genes such as DNMT3A, ASXL1, IDH1/2, and TET2. Next-generation sequencing analysis of a mother and son pair who both developed adult-onset diploid AML identified a novel germline missense mutation DNMT3A p.P709S. The p.P709S protein-altering variant resides in the highly conserved catalytic DNMT3A methyltransferase domain. Functional studies demonstrate that the p.P709S variant confers dominant negative effects when interacting with wildtype DNMT3A. LINE-1 pyrosequencing and reduced representation bisulphite sequencing (RBBS) analysis demonstrated global DNA hypomethylation in germline samples, not present in the leukaemic samples. Somatic acquisition of IDH2 p.R172K mutations, in concert with additional acquired clonal DNMT3A events in both patients at the time of AML diagnosis, confirms the important pathogenic interaction of epigenetically active genes, and implies a strong selection and regulation of methylation in leukaemogenesis. Improved characterization of germline mutations may enable us to better predict malignant clonal evolution, improving our ability to provide customized treatment or future preventative strategies.

摘要

急性髓系白血病 (AML) 是一种异质性髓系恶性肿瘤，其特征是反复发生克隆事件，包括表观遗传相关基因如DNMT3A、ASXL1、IDH1/2和TET2的突变。对均发生成人发病二倍体 AML 的母子对的下一代测序分析确定了一种新的种系错义突变DNMT3A p.P709S。p.P709S 蛋白改变变体位于高度保守的催化 DNMT3A 甲基转移酶结构域中。功能研究表明，p.P709S 变体在与野生型DNMT3A相互作用时会产生显着的负面影响. LINE-1 焦磷酸测序和减少代表性亚硫酸氢盐测序 (RBBS) 分析表明，生殖系样本中的整体 DNA 低甲基化，在白血病样本中不存在。IDH2 p.R172K 突变的体细胞获得，与 AML 诊断时两名患者的额外获得性克隆 DNMT3A 事件一致，证实了表观遗传活性基因的重要致病相互作用，并暗示白血病发生中甲基化的强烈选择和调节。改进种系突变的表征可能使我们能够更好地预测恶性克隆进化，提高我们提供定制治疗或未来预防策略的能力。