Function of ADAR1 in Hematopoietic and Leukemia Stem Cells

项目描述（申请人提供）：本项目旨在定义作用于RNA 1的RNA编辑酶腺苷脱氨酶（ADAR1）在造血和白血病干细胞中的功能。特别是这些干细胞对ADAR1 RNA编辑活性的要求将被确定。ADAR1是胚胎和成人造血所必需的蛋白，而白血病细胞更容易受到ADAR1编码基因缺失的影响。虽然在ADAR1缺失的情况下，移植的造血干细胞（HSC）在受者体内的造血再生受到抑制，但归巢和自我更新能力是完整的。大量细胞死亡只发生在分化的祖细胞中。此外，在小鼠白血病模型中发现，去除ADAR1会导致所有治疗动物在一周内大量白血病细胞死亡，包括白血病干细胞/祖细胞。描述ADAR1对正常和白血病干细胞（LSC）的不同影响可能有助于揭示白血病干细胞的特征，并导致白血病治疗的分子靶点的发现。该项目的目标是描述ADAR1对正常和LSC的不同影响，并开发一种靶向ADAR1消除白血病干细胞的治疗策略。尽管ADAR1被鉴定为一种RNA编辑酶，并且RNA编辑已被证明在干细胞和其他生物过程中发挥关键作用，但迄今为止的多次尝试都无法确定ADAR1敲除后正常造血细胞和白血病细胞死亡的编辑靶标。在缺乏已知的因果编辑转录本的情况下，确定ADAR1对白血病和LSCs的作用需要rna编辑是具有挑战性的，特别是因为最近已经描述了ADAR1的编辑独立功能。这里假设ADAR1的RNA编辑活性不能解释其在白血病细胞中的功能。本提案旨在寻求ADAR1的编辑活性是否为LSCs的增殖和分化所必需的明确答案。因此，该项目将首先生成一个敲入（KI）小鼠模型，在该模型中，从突变的内源性ADAR1基因中表达无活性的用于RNA编辑的ADAR1。然后在ADAR1 KI动物中分析失活ADAR1对造血和LSCs的影响。将观察HSC和LSC以及成熟细胞，并将其与野生型和ADAR1敲除细胞进行比较。从这个项目中获得的知识将有助于了解LSC和白血病的发展，并最终有助于改善白血病的治疗。

DESCRIPTION (provided by applicant): This project is to define the function of RNA editing enzyme adenosine deaminase acting on RNA 1 (ADAR1) in hematopoietic and leukemia stem cells. Particularly the requirement of RNA editing activity of ADAR1 in these stem cells will be determined. ADAR1 is an essential protein for embryonic and adult hematopoiesis, while the leukemia cells are more susceptible to the gene deletion that codes ADAR1. Whereas hematopoietic repopulation in the recipients by transplanted hematopoietic stem cell (HSC) is suppressed in the absence of ADAR1, the homing and self-renewal capacities are intact. Massive cell death only occurred in the differentiating progenitor cells. Moreover, it have been found in a mouse leukemia model removal of ADAR1 causes massive leukemia cell death including the leukemia stem/progenitor cells within one week in all the treated animals. Delineation of the discrepant impacts of ADAR1 on normal and leukemia stem cells (LSC) might shed a light on the characterization of the leukemia stem cells and lead to a discovery of a molecular target for leukemia treatment. The goal of this project is to delineate the different impacts of ADAR1 on normal and LSC and develop a therapeutic strategy to eliminate leukemia stem cells by targeting ADAR1. Although ADAR1 is identified as an RNA editing enzyme and RNA editing has been shown to play critical roles in stem cells and other biological processes, multiple attempts to date have been unable to identify an editing target that accounts for the death of normal hematopoietic and leukemia cells of ADAR1 knockouts. It is challenging to determine RNA-editing is required for ADAR1's effects on leukemia and LSCs in the absence of a known causal edited transcript, particularly because editing-independent functions fo ADAR1 have recently been described. It is hypothesized here that the RNA editing activity of ADAR1 does not account for its function in leukemia cells. This proposal is to seek a definitive answer whether the editing activity of ADAR1 is necessary for the proliferation and differentiation of LSCs. Therefore this project will first generate a Knock-In (KI) mouse model in which an inactive ADAR1 for RNA editing is expressed from mutated endogenous ADAR1 gene. Then the impact of inactive ADAR1 on the hematopoietic and LSCs will be analyzed in the ADAR1 KI animals. HSC and LSC as well as the mature cells will be observed and compared to wild type and ADAR1 knockout cells. The knowledge obtained from this project will help to understand the LSC and leukemia development and eventually contribute to improve the leukemia treatment.