The impact of increased mutation burden on promoting clonal hematopoiesis

项目总结/摘要 体细胞突变发生在造血干细胞（HSC）的整个生命。偶然的，突变可能会破坏 一个关键基因，并赋予突变HSC竞争优势，导致其克隆后代的扩增。 这种现象被称为克隆造血（CH），随着年龄的增长而普遍存在。CH相关 血液恶性肿瘤、心血管和肺部疾病、II型糖尿病的风险升高， 全因死亡率几乎所有50岁以上的成年人都携带有白血病突变的CH克隆- 相关基因，但这些突变体克隆包含非常低的总血细胞分数，因此， 推测是功能惰性的。越来越多的文献表明，在大多数人中，低频率 突变克隆血液组分随时间保持稳定。然而，没有模型可以捕捉 这些随机产生的低频率克隆。因此，是否驱动突变采集和足够的时间 最终会导致克隆扩张仍是未知数。本提案的目的是确定 其基础HSC突变负荷和CH驱动程序的获得足以进行克隆扩增， 时间初步计算预测，每个编码基因在HSC库中突变约70次， 这表明CH驱动基因的突变是长寿不可避免的。相比之下， 在小鼠模型中从未报道过CH，可能是因为小鼠的HSC较少，寿命有限 在此期间获得HSC突变。这一提议的核心假设是， 出现是足够的突变率和时间的产物。我将用两只老鼠来评估这个假设。 随机突变获取模型。目标1中提出的实验将询问老年野生型小鼠， 确定独立于寿命的高龄在多大程度上促进CH的发展。 将在实验上提高鼠HSC中的整体突变负荷，以确定随机获得是否 CH驱动突变将导致突变克隆扩张随着时间的推移，以及老化的环境如何影响CH 发展实验将确定促进克隆的突变负荷和时间的充分性。 造血，并将决定在克隆扩张中的作用的一个老化的微环境。总的来说，这项工作 可能揭示通过调节突变克隆生长来增强健康衰老的策略。

PROJECT SUMMARY/ABSTRACT Somatic mutations occur in hematopoietic stem cells (HSCs) throughout life. By chance, a mutation may disrupt a key gene and confer a competitive advantage on the mutant HSC, leading to expansion of its clonal progeny. This phenomenon is called clonal hematopoiesis (CH) and is ubiquitous with increasing age. CH is associated with elevated risk for hematological malignancy, cardiovascular and pulmonary diseases, type II diabetes, and overall all-cause mortality. Nearly all adults older than 50 years harbor CH clones with mutations in leukemia- associated genes, but these mutant clones comprise a very low fraction of total blood cells and thus are speculated to be functionally inert. A growing body of literature indicates that, in most individuals, low-frequency mutant clonal blood fractions remain stable over time. However, no models exist that capture the behavior of these stochastically arising low-frequency clones. Thus, whether driver mutation acquisition and adequate time will lead to eventual clonal expansion remains unknown. The goal of this proposal is to determine the extent to which underlying HSC mutation burden and acquisition of CH drivers are sufficient for clonal expansion over time. Preliminary calculations predict every coding gene is mutated about 70 times in the HSC pool during an average human lifespan, indicating mutation in a CH driver gene is inevitable with longevity. In contrast, native CH has never been reported in murine models, possibly because mice have fewer HSCs and a limited lifespan during which to acquire HSC mutations. The central hypothesis of this proposal is that clonal hematopoiesis emergence is the product of sufficient mutation rate and time. I will evaluate this hypothesis using two murine models for stochastic mutation acquisition. Experiments proposed in Aim 1 will query aged wild-type mice to determine the extent that advanced age, independent of lifespan, promotes the development of CH. In Aim 2, I will experimentally elevate the global mutation burden in murine HSCs to determine if the stochastic acquisition of a CH driver mutation will lead to mutant clonal expansion over time, and how an aged milieu impacts CH development. The experiments will define the sufficiency of mutation burden and time for promoting clonal hematopoiesis and will determine the role of an aged microenvironment in clonal expansion. Overall, this work may uncover strategies to enhance healthy aging via modulation of mutant clonal outgrowth.