The role of DNMT3A in gene regulation and stem cell expansion

项目总结 DNA甲基化是一种表观遗传修饰，在调节干细胞方面起着关键作用， 发展和许多疾病。在癌症中观察到DNA甲基化异常已有更多 二十多年来，许多研究都集中在启动子的超甲基化上，这种甲基化是沉默的 肿瘤抑制基因。此外，DNMT3A，从头DNA甲基转移酶之一，是 在一系列血液系统恶性肿瘤中经常发生突变。我们的实验室已经证明 DNMT3A缺失损害了造血干细胞(HSC)的分化，同时使HSC数量增加 提示DNMT3A可能在肿瘤发生和干细胞调节中发挥作用。 然而，白血病患者样本的DNA甲基化图谱显示DNA甲基化与 整个基因组的基因表达很差，突出了我们对特定基因的有限理解 DNA甲基化的功能。最近使用最常见的DNMT3A小鼠模型的研究 血液系统恶性肿瘤中的突变DNMT3AR882表明DNMT3AR882具有协同作用 与Flt3--ITD和NPM1c突变有关的突变有助于白血病转化。尽管如此，我们的 了解哪些剩余的DNMT3A突变会导致白血病的发生及其机制 它们在癌症形成中所起的作用仍然缺乏。因此，世界银行的长期目标是 拟议的研究是为了了解DNMT3A如何影响癌症中的基因调控，以及如何 DNMT3A突变体使干细胞易于扩张。在目标1中，我建立了一个新的dna表观基因组 用于研究DNA之间因果关系的编辑工具(dCas9-Suntag-DNMT3A系统) 甲基化和基因表达。使用全基因组图谱的泛癌症分析，我们有 发现在峡谷(宽阔的和 甲基化不足的区域)，并激活相应的基因表达。在Aim 2中，使用 我建立的DNMT3A突变小鼠模型，我将阐明一个DNMT3A突变在启动中的作用 干细胞扩增。这项拟议研究的发现将有助于揭示异常DNA 癌症中的甲基化与DNMT3A相关恶性肿瘤的分子机制小才是 已知表观遗传修饰物的突变如何影响癌症的3D基因组结构。 因此，在目标3中，我计划利用我的博士后研究来了解表观遗传学修饰物是如何 塑造癌症的基因组图景及其潜在机制。这一培训计划是 为我量身定做的基础科学研究的全面教育将是非常有用的 实现我成为一名独立癌症研究人员的长期职业目标。

PROJECT SUMMARY DNA methylation is an epigenetic modification that plays a key role in regulating stem cells, development and many diseases. Abnormal DNA methylation has been observed in cancer for more than two decades, with many investigations focusing on promoter hypermethylation, which silences tumor suppressor genes. Additionally, DNMT3A, one of de novo DNA methyltransferases, is frequently mutated in a spectrum of hematological malignancies. Our lab has demonstrated that Dnmt3a loss impairs hematopoietic stem cell (HSC) differentiation, while expanding HSC numbers in bone marrow, suggesting DNMT3A may have a role in tumorigenesis and stem cell regulation. However, DNA methylation profiling of leukemia patient samples shows DNA methylation correlates poorly with gene expression across the genome, highlighting our limited understanding of the specific functions of DNA methylation. Recent studies using a murine model of the most frequent DNMT3A mutation in hematological malignancies, DNMT3AR882, demonstrated that DNMT3AR882 cooperates with FLT3-­ITD and NPM1c mutations to contribute to leukemic transformation. Nevertheless, our knowledge of which remaining DNMT3A mutations lead to leukemogenesis and the mechanisms by which they contribute to cancer formation remains lacking. Therefore, the long-­term goal of the proposed research is to understand how DNMT3A affects gene regulation in cancer, and how DNMT3A mutants predispose stem cell expansion. In Aim 1, I established a novel DNA epigenome editing tool (dCas9-­SunTag-­DNMT3A system) to investigate the causal relationship between DNA methylation and gene expression. Using pan-­cancer analysis of genome-­wide profiles, we have identified DNA hypermethylation occurring in the gene-­body regions of canyons (broad and undermethylated regions) with activation of corresponding gene expression. In Aim 2, using a Dnmt3a mutant murine model I developed, I will elucidate the role of one Dnmt3a mutant in priming stem cell expansion. The findings from this proposed research will shed the light on abnormal DNA methylation in cancer and molecular mechanisms of DNMT3A-­associated malignancies. Little is known about how mutations in epigenetic modifiers affect the 3D genomic structure in cancer. Therefore, in Aim 3, I plan to use my postdoctoral studies to understand how epigenetic modifiers shape the genomic landscape in cancer and their underlying mechanism. This training program is tailored to give me a comprehensive education in basic science research that will be extremely useful in achieving my long-­term career goal of becoming an independent cancer researcher.