A Mouse Model of DNMT3A-Associated Hematologic Malignancy

描述（由申请人提供）：新生DNA甲基转移酶3A （DNMT3A）突变与多种血液恶性肿瘤相关，包括髓性和淋巴性白血病；然而，这种突变促进其发展的机制尚不清楚。小鼠造血干细胞（HSC）中Dnmt3a功能的缺失导致HSC急剧扩增并抑制分化，而不会发生白血病，这表明其他基因共同发生的突变对白血病的发展很重要。在这里，我们的总体目标是深入了解潜在的病理生理机制，通过DNMT3A突变改变疾病的过程，给出其他类似的突变概况。我们假设Dnmt3a缺失通过阻止干细胞自我更新基因的抑制、抑制分化和扩大靶细胞群，从而使干细胞和/或早期祖细胞转化为致敏细胞。我们预计细胞环境，如细胞类型、年龄和甲基化丢失程度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突变如何导致一系列恶性肿瘤。为了实现这一目标，我们将使用Dnmt3a-FLT3-ITD模型研究突变类型对髓系与淋巴系恶性肿瘤产生的影响。将FLT3-ITD引入dnmt3a突变的造血干细胞和祖细胞中，检测所产生疾病的类型和潜伏期。我们还将研究在老化方面的有机环境的作用。此外，我们将研究协同FLT3突变的靶细胞类型对疾病结果的影响。最后，我们将探讨Dnmt3a突变加速和改变FLT3-ITD表达影响的机制。具体而言，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谱和基因表达模式。甲基化改变也将与在类似的人类白血病中发现的DNMT3A突变进行比较。最终，这些数据将使我们能够广泛地确定DNA甲基化的作用，以及在人类白血病发展中的特定位点。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DNMT3A相关恶性肿瘤的新治疗方法的开发。

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.