A Mouse Model of DNMT3A-Associated Hematologic Malignancy

描述(由申请人提供)：从头DNA甲基转移酶3A(DNMT3A)突变与多种血液系统恶性肿瘤有关，包括髓系白血病和淋巴细胞性白血病；然而，这些突变促进其发展的机制尚不清楚。小鼠造血干细胞(HSCs)中DNMT3A功能的丧失导致HSC的急剧扩张并抑制分化，而不是单纯的白血病，这表明其他基因的共生突变在白血病发生中的重要性。在这里，我们的首要目标是深入了解潜在的病理生理机制，通过这些机制，DNMT3A突变改变了疾病的进程，在其他方面具有类似的突变特征。我们假设，DNMT3A丢失通过阻止抑制干细胞自我更新基因，抑制分化，并扩大靶细胞群，然后使其对二次致癌打击的影响敏感，从而启动干细胞和/或早期祖细胞的转化。我们预计细胞环境，就细胞类型、年龄和甲基化缺失程度而言，会影响白血病的类型。通过使用我们的小鼠模型研究DNMT3A突变的作用，我们希望阐明DNMT3A突变是如何导致一系列恶性肿瘤的。为了达到这个目标，我们将使用DNMT3A-Flt3-ITD模型研究突变类型对髓系和淋巴系恶性肿瘤发生的影响。Flt3-ITD将被引入DNMT3A突变的造血干细胞和祖细胞中，并将检测产生的疾病类型和潜伏期。我们还将研究生物环境在衰老方面的作用。此外，我们还将检查协同作用的Flt3突变的靶细胞类型对疾病结局的影响。最后，我们将探讨DNMT3A突变加速和改变Flt3-ITD表达的机制。具体地说，将比较具有和不具有DNMT3A突变的类似恶性肿瘤的全基因组甲基化情况和基因表达模式。甲基化改变也将与在携带DNMT3A突变的类似人类白血病中发现的甲基化改变进行比较。最终，这些数据将使我们能够广泛地确定DNA甲基化在人类白血病发生中的作用，并在特定的位置上。总之，这些方法将有助于深入了解DNMT3A突变促进各种人类血液系统恶性肿瘤的方式，并导致开发新的治疗DNMT3A相关恶性肿瘤的方法。

DESCRIPTION (provided by applicant): Mutations of the de novo DNA methyltransferase 3A (DNMT3A) are associated with multiple hematologic malignancies, including both myeloid and lymphoid leukemias; however, the mechanisms through which such mutations contribute to their development is obscure. Loss of Dnmt3a function in murine hematopoietic stem cells (HSCs) led to dramatic HSC expansion and inhibited differentiation without frank leukemia suggesting the importance of co-occurring mutations in other genes for leukemia development. Here, our overarching goal is to gain insight into the underlying pathophysiologic mechanisms through which DNMT3A mutations alter the course of disease given an otherwise similar mutational profile. We hypothesize that Dnmt3a loss primes stem cells and/or early progenitors for transformation by preventing the repression of stem cell self-renewal genes, inhibiting differentiation, and expanding a target cell population that is then sensitized to the impact of secondary oncogenic hits. We expect that the cellular milieu, in terms of cell type, age, and degree of methylation loss influences the type of leukemia that develops. By investigating the role of Dnmt3a mutations using our mouse model, we hope to elucidate how DNMT3A mutations contribute to an array of malignancies. Toward this goal, we will examine the influence of the mutation type on the generation of myeloid versus lymphoid malignancies using a Dnmt3a-FLT3-ITD model. FLT3-ITD will be introduced into Dnmt3a-mutant HSCs and progenitors and the type and latency of disease generated will be examined. We will also examine the role of the organismal milieu in terms of aging. In addition, we will examine the influence of the target cell type of cooperating FLT3 mutations on the disease outcome. Finally, the mechanism through which Dnmt3a mutation accelerates and alters the impact of FLT3-ITD expression will be examined. Specifically, the whole genome methylation profile and gene expression patterns of similar malignancies with and without Dnmt3a mutations will be compared. Methylation alterations will also be compared with those found in similar human leukemias harboring DNMT3A mutations. Ultimately, these data will allow us to identify the role of DNA methylation broadly, and at specific loci in human leukemia development. Together, these approaches will lend insight into the manner in which DNMT3A mutations promote a variety of human hematologic malignancies and lead to development of new therapeutic approaches for DNMT3A-associated malignancies.