Inflammatory Stress Promotes Clonal Expansion of DNMT3A-mutant HSCs

摘要 血液疾病，如骨髓增生异常综合征(MDS)，由造血干细胞(HSCs)引起 获得破坏关键的HSC功能的基因突变。最频繁变异的物种之一 这些肿瘤中的基因是从头DNA甲基转移酶DNMT3A。然而，DNMT3A 在临床表现出现之前很久，造血干细胞就会发生突变。最近的研究表明，HSC 随着年龄增长而占主导地位的克隆通常含有髓系肿瘤特有的突变。这 这种现象被称为克隆性造血(CH)，但只有一小部分CH患者会继续 患上血液病。这表明，除了遗传因素，一定还有其他因素在起作用。 选择繁殖带有这些突变的造血干细胞的个体之间存在差异。我们的实验室有兴趣 在确定可能为这些突变克隆提供选择压力的随年龄变化的因素时， 专注于炎症。之前的资助期确定干扰素伽马(IFNG)是一种环境 选择DNMT3A突变的HSCs生长的压力源。虽然慢性IFNG信号对 正常的造血干细胞，DNMT3A突变的造血干细胞的功能在这种情况下被保留，呈现出一种机制 因此，具有这些突变的造血干细胞在炎症环境中获得克隆性优势。中生成的新数据 我们的实验室表明，DNMT3A突变的HSC不仅在体内对IFNG的有害影响具有抵抗力，而且 此外，突变克隆自身也会产生更多的IFNG来应对炎症。这与以下内容相关 突变克隆的Cxcl9表达增加，T细胞向骨髓的渗透增加。这些观察结果形成 这次续签申请的科学前提。我们推测由DNMT3A突变产生的IFNG 克隆抑制其他HSC基因型，并通过T细胞渗透重塑生态位以进一步强化 他们的竞争优势。我们提出了以下具体目标来调查这些问题； 确定DNMT3A突变克隆的IFNG生产是否加剧了它们的竞争力 优势。 确定DNMT3A突变克隆是否重塑了BM生态位。 检查了DNMT3A突变细胞的细胞和分子机制 对IFNG过敏。 这项工作的总体目标是确定炎症信号促进克隆的机制 DNMT3A突变的造血干细胞在骨髓中的扩增。消除或选择性抑制的方法 来自高危CH+个体的新出现的DNMT3A突变HSC克隆可能为干预提供一个窗口 在突变细胞能够建立克隆优势并进化为暴发性疾病之前。

ABSTRACT Blood diseases such as myelodysplastic syndromes (MDS) arise from hematopoietic stem cells (HSCs) that acquire genetic mutations which corrupt critical HSC functions. One of the most recurrently mutated genes in these neoplasms is the de novo DNA methyltransferase enzyme DNMT3A. However, DNMT3A mutations can occur in HSCs long before clinical presentation. Recent studies have shown that the HSC clones that predominate with age often contain mutations that are characteristic of myeloid neoplasms. This phenomenon is known as clonal hematopoiesis (CH), but only a small fraction of individuals with CH go on to develop a blood disease. This suggests that in addition to genetics, there must be other factors which act differently between individuals that select for propagation of HSCs with these mutations. Our lab is interested in identifying factors that change with age which may provide selective pressures for these mutant clones, focusing on inflammation. The prior funding period identified interferon gamma (IFNg) as an environmental stressor that selects for the outgrowth of Dnmt3a-mutant HSCs. While chronic IFNg signaling is detrimental to normal HSCs, functionality of Dnmt3a-mutant HSCs is preserved in this setting, presenting a mechanism whereby HSCs with these mutations gain clonal dominance in settings of inflammation. New data generated in our lab show that Dnmt3a-mutant HSCs are not only resistant to the detrimental effects of IFNg in vivo, but also the mutant clones produce more IFNg themselves in response to inflammation. This is associated with increased Cxcl9 expression from the mutant clones and T-cell infiltration into the BM. These observations form the scientific premise for this renewal application. We hypothesize that IFNg production by Dnmt3a-mutant clones suppresses other HSC genotypes and remodels the niche through T-cell infiltration to further reinforce their competitive advantage. We propose the following Specific Aims to investigate these questions;  Determine if IFNg production from Dnmt3a-mutant clones exacerbates their competitive advantage.  Determine if Dnmt3a-mutant clones remodel the BM niche.  Examine the cellular and molecular mechanisms by which Dnmt3a-mutant cells are hypersensitive to IFNg. The overall goal of this work is to determine the mechanisms by which inflammatory signals promote clonal expansion of Dnmt3a-mutant HSCs in the bone marrow. Approaches to eliminate or selectively inhibit emerging DNMT3A-mutant HSC clones from high-risk CH+ individuals may provide a window for intervention before the mutant cells are able to establish clonal dominance and evolve to fulminant disease.