Characterization of functional heterogeneity in a mouse model of HoxA9/Meis1 dependent acute myeloid leukemia through fluorescent genetic barcoding.

急性髓性白血病（AML）是一种严重的造血系统疾病，长期生存率低。其原因在于标准疗法无法完全根除白血病干细胞（LSC）群。为了研究这种疾病，模拟人类AML的小鼠模型是至关重要的。其中一种模型依赖于移植过表达HoxA9和Meis1 （H9M）转录因子的小鼠骨髓细胞。根据目前的文献，H9M LSC库包含至少三个表型定义的亚群，这些亚群彼此克隆重建，并在连续移植后产生整个白血病等级。然而，我们自己的数据表明，这些表型定义的LSC可能是分层组织的。鉴于已报道的LSC亚群的药物敏感性差异，了解控制LSC特性的分子途径及其在健康造血中的特征可能为更好的治疗选择铺平道路。因此，本提案的目标为1。表征调控H9M LSC表型特性和表型可塑性的转录程序和信号通路；2. 确定可增加疾病侵袭性并可能适合作为预后指标的H9M合作伙伴；和3。研究Aims 1和Aims 2中白血病相关基因对健康造血的功能意义。这些研究的关键将是利用新开发的慢病毒基因标记系统来唯一标记多达12个细胞群。因此，这种方法提供了直接监测和比较同一只小鼠中多个H9M种群命运的机会，同时减少了所需的小鼠数量。基于这一策略，我们将首先采用多重移植分析来深入了解H9M LSC池的分层组织。然后，我们将利用比较分子研究和功能研究来表征控制单个LSC群体表型并可能控制其等级组织的基因表达途径。我们进一步假设慢病毒基因标记可能通过触发与H9M信号合作的继发性遗传病变来影响LSC特征。这些罕见的突变体将通过多重H9M移植试验和随后的整合位点分析来鉴定。在研究白血病相关基因在健康造血中的功能（如转化潜力、自我更新能力和谱系偏斜）之前，将通过询问公开可用的数据集（TCGA）来评估实验验证的H9M合作伙伴对患者生存的预后价值。因此，这项工作将导致识别和表征控制LSC特性的机制，这可能有助于LSC定向治疗的发展，以提高患者的生存率。

Acute myeloid leukemia (AML) is a severe hematopoietic disease with low long-term survival rates. The reason for this lies in the failure of standard therapies to fully eradicate the leukemic stem cell (LSC) population. For studying the disease, mouse models mimicking human AML are of utmost importance. One of these models relies on the transplantation of murine bone marrow cells overexpressing HoxA9 and Meis1 (H9M) transcription factors. According to current literature, the H9M LSC pool contains at least three phenotypically defined subpopulations that clonally reconstitute each other and that give rise to the whole leukemic hierarchy upon serial transplantation. However, our own data indicate that these phenotypically defined LSC may be hierarchically organized. Given the reported differences in drug sensitivities of the LSC subpopulations, understanding the molecular pathways that govern LSC properties, and their characterization in healthy hematopoiesis may pave the way for better treatment options. Therefore, this proposal aims at 1. Characterizing transcription programs and signaling pathways that regulate the phenotypic identity as well as the phenotypic plasticity of H9M LSC; 2. Identifying H9M collaboration partners that increase the aggressiveness of the disease and may be suitable as prognostic markers; and 3. Investigating the functional implications of leukemia associated genes from Aims 1 and 2 for healthy hematopoiesis. Key to these studies will be the utilization of a newly developed lentiviral gene marking system for uniquely labeling of up to 12 cell populations. This approach thus offers the opportunity to directly monitor and compare the fate of multiple H9M populations in the same mouse, while concomitantly reducing required mouse numbers. Based on this strategy, we will first employ multiplex transplantation assays to gain deeper insights into the hierarchical organization of the H9M LSC pool. We will then utilize comparative molecular studies and functional studies for characterizing gene expression pathways that control the phenotype of individual LSC populations and potentially govern their hierarchical organization. We furthermore hypothesize that lentiviral gene marking may influence LSC features by triggering secondary genetic lesions that collaborate with H9M signaling. These rare mutants will be identified through multiplex H9M transplantation assays and subsequent integration site analyses. The prognostic value of experimentally verified H9M collaboration partners on patient survival will then be assess by interrogating publicly available data sets (TCGA), before investigating the function of leukemia associated genes in healthy hematopoiesis, e.g. transformation potential, self-renewal capacity and lineage skewing. This work will thus lead to the identification and characterization of mechanisms controlling LSC properties, which may aid the development of LSC directed therapies for improving patient survival.