H3K79 Methylation in Hematopoietic Stem Cell Development and MLL-Rearranged Leuk

描述(由申请人提供)：我提出了一个为期5年的职业发展计划，旨在了解表观遗传学变化在正常造血发育和MLL重排白血病中的作用，同时建立在造血干细胞移植方面的学术生涯。我将在我在分子生物学和临床血液学/肿瘤学方面的坚实基础上，在斯图尔特·奥尔金博士和斯科特·阿姆斯特朗博士的领导下，发展表观遗传调节、造血干细胞和白血病生物学方面的专业知识。奥尔金博士是造血发展和全基因组遗传、表观遗传学和蛋白质组学研究的先驱和世界领先者。阿姆斯特朗博士在MLL重排白血病的基因组方法和表观遗传学变化方面是世界领先者。近年来，表观遗传修饰已经开始被认为是一个动态的和精细调控的过程，涉及转录控制和主要细胞命运的决定。组蛋白甲基转移酶DOT1L负责组蛋白3赖氨酸79(H3K79)的甲基化，最近被认为是混合系白血病(MLL)基因重排的重要组成部分。未发表的数据也指出了在早期造血发育中的基础作用。我们已经建立了DOT1L的条件性功能丧失小鼠模型，我们将使用该模型直接研究DOT1L在造血和白血病中的作用。在特定的目标1中，我们将表征DOT1L在造血发育和稳定状态成人造血过程中失活的造血表型。我们将通过一系列的遗传和移植实验，在体外和体内评估胚胎造血发育、干细胞和祖细胞频率、自我更新和分化。我们还将在全基因组水平上研究H3K79甲基化缺失如何影响造血干细胞中的其他染色质修饰。在特定的目标2中，我们将检验这样的假设，即通过MLL融合蛋白错误募集DOT1L是MLL介导的白血病发生的基本步骤，并且是白血病细胞生存所必需的。为此，我们将评估在我们的条件DOT1L基因敲除小鼠模型中，常见的融合MLL-AF4和MLL-AF9诱导的白血病的发生和维持。我们将在人类MLL重排的白血病细胞中进行DOT1L sh-RNA击倒实验。此外，我们计划利用我们的模型与Stuart Schreiber博士合作验证DOT1L潜在的小分子抑制剂。这些目标的实现将阐明染色质调节在良性和恶性造血中的基本机制。

DESCRIPTION (provided by applicant): I present a 5-year career development plan that seeks to understand the role of epigenetic changes in normal hematopoietic development and MLL-rearranged leukemia, while establishing an academic career in Hematopoietic Stem Cell Transplantation. I will build on my strong foundation in molecular biology and clinical hematology/oncology to develop expertise in epigenetic regulation, hematopoietic stem cell, and leukemia biology under the leadership of Dr. Stuart Orkin and Dr. Scott Armstrong. Dr Orkin is a pioneer and world leader in hematopoietic development and genome wide genetic, epigenetic and proteomic studies. Dr Armstrong is a world leader in genomic approaches and epigenetic changes in MLL rearranged leukemias. In the recent years, epigenetic modifications have started to be recognized as a dynamic and finely regulated processe involved in transcriptional control and major cell fate decisions. The histone methyl transferase Dot1l, which methylates histone 3 at lysine 79 (H3K79), has recently been implicated as a crucial component in mixed lineage leukemia (MLL) gene rearranged leukemias. Unpublished data also point to a fundamental role in early hematopoietic development. We have generated a conditional loss of function mouse model for Dot1l, and we will use this model to directly address the role of Dot1l in hematopoiesis and leukemia. In specific aim 1 we will characterize the hematopoietic phenotype of Dot1l inactivation during hematopoietic development and steady state adult hematopoiesis. We will assess embyonic hematopoietic development, stem and progenitor cell frequencies, self-renewal and differentiation in vitro and in vivo through a series of genetic and transplantation experiments. We will also investigate how loss of H3K79 methylation affects other chromatin modifications in hematopoietic stem cells on a genome wide level. In specific aim 2 we will test the hypothesis that mis-recruitment of DOT1L through MLL-fusion proteins is a fundamental step in MLL-mediated leukemogenesis, and required for leukemia cell survival. To this end, we will assess the development and maintenance of leukemia induced by the common fusions Mll-Af4 and Mll-Af9 in our conditional Dot1l knockout mouse model. We will conduct DOT1L sh-RNA knock down experiments in human MLL-rearranged leukemia cell. In addition, we plan to utilize our models to validate potential small molecule inhibitors for DOT1L in collaboration with Dr. Stuart Schreiber. Execution of these aims will elucidate fundamental mechanisms of chromatin regulation in benign and malignant hematopoiesis.