Deciphering Critical Changes in the Methylome of Hematopoietic Stem Cells in Age-related Clonal Hematopoiesis and Myeloid Leukemogenesis

发生急性髓性白血病（AML）的危险因素之一是较高的年龄。考虑到在西方世界，65岁及以上的个体预计还能再存活大约20年，AML对这一年龄组的生存造成了毁灭性的影响。其中一个关键问题一直是，并且仍然是，哪些确切的机制导致老年人AML的急剧增加。一些独立报告表明，衰老与克隆造血的发展有关，所谓的“年龄相关克隆造血”（age-related clonal hematopoiesis， ARCH）显著增加了受影响个体发生血液学肿瘤的可能性。这些临床意义导致了一种新的疾病的提出，称为“不确定潜力的克隆造血”（CHIP），它描述了携带已知在血液恶性肿瘤中反复突变的基因突变的健康个体。重要的是，CHIP与表观遗传修饰因子的突变有关。在我们的建议中，我们假设来自非克隆造血的年轻造血干细胞与来自克隆造血的老年造血干细胞、来自克隆造血的老年造血干细胞和来自老年AML患者的LSCs之间的DNA甲基化组存在关键变化，这些LSCs携带已知的驱动克隆造血的突变。首先，数据显示了从年轻人到老年人的年龄依赖性全球DNA甲基化模式。在即将到来的资助期内，我们将通过RNA-Seq将全球DNA甲基化分析与个体样本中的转录组联系起来。我们将进一步通过单细胞测序来表征克隆型和非克隆型造血干细胞的转录组和甲基组，并将该分析扩展到以白血病干细胞和残余造血干细胞嵌合体为特征的原发性AML样本，这些造血干细胞有或没有年龄相关突变。这些数据将通过功能分析加以补充，测试候选基因（如同源盒基因）在体内CHIP发育中的作用。

One of the risk factors for developing acute myeloid leukemia (AML) is higher age. Considering that in the Western world, individuals aged 65 and older, are expected to survive approximately another 20 years, AML has a devastating impact on the survival of this age group. One of the key questions has been, and still is, which precise mechanisms lead to the steep increase in AML in the elderly. Several independent reports have demonstrated that aging is associated with the development of clonal hematopoiesis and that so called “age-related clonal hematopoiesis” (ARCH) significantly increases the probability of affected individuals to develop hematological neoplasias. These clinical implications have led to the proposal of a new disorder called “clonal hematopoiesis of indeterminate potential” (CHIP), which describes healthy individuals carrying mutations in genes known to be recurrently mutated in hematological malignancies. Importantly, CHIP is associated with mutations in epigenetic modifiers. In our proposal we hypothesize that there are critical changes in the DNA methylome between young versus aged HSCs derived from non-clonal hematopoiesis, aged HSCs from clonal hematopoiesis and LSCs from elderly patients with AML carrying mutations known to drive clonal hematopoiesis. First data indicate age-dependent global DNA methylation patterns from young to old. In the upcoming funding period, we will link global DNA methylation profiling with transcriptomes in the individual samples by RNA-Seq. We will furthermore characterize the transcriptome and methylome of clonal versus non-clonal HSCs by single cell sequencing and extend this analysis to primary AML samples characterized by a mosaique of leukemic stem cells and residual HSCs with and without age-related mutations. These data will be complemented by functional analyses, testing the role of candidate genes such as homeobox genes on development of CHIP in vivo.