The role of Kmt2c/MLL3 in hematopoietic stem cell self-renewal, commitment and exhaustion

Kmt2c/MLL3 在造血干细胞自我更新、承诺和耗竭中的作用

基本信息

批准号：
10594950
负责人：
Jeffrey Alan Magee
金额：
$ 39.38万
依托单位：
WASHINGTON UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
2020
资助国家：
美国
起止时间：
2020-04-01 至 2024-03-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/10594950
关键词：
ATAC-seq Adult Alleles Archives Binding Blood Cell Cycle Kinetics ChIP-seq Chromatin Chromosome Deletion Data Enhancers Exposure to Family Follow-Up Studies Gene Expression Genes Genetic Enhancer Element Genetic Transcription Genetically Engineered Mouse Goals Hematopoietic stem cells Human Inflammation Inflammatory Interleukin-1 Life MAPK8 gene Marrow Methyltransferase Mus Mutate Mutation Myelogenous Recording of previous events Recovery Regulation Risk Role SET Domain Signal Transduction Stress Structure Testing Zinc Fingers anakinra chemotherapy clinically relevant cytokine design exhaustion hematopoietic stem cell differentiation hematopoietic stem cell self-renewal histone methyltransferase insight interleukin-18 receptor leukemia leukemogenesis loss of function mutant preservation prevent programs response self-renewal stem cell function stem cells transcription factor transplantation therapy

项目摘要

PROJECT SUMMARY The goal of this proposal is to understand how KMT2C/MLL3 regulates hematopoietic stem cell (HSC) self- renewal and why KMT2C mutations convey a selective advantage that can lead to leukemia. KMT2C encodes MLL3, a COMPASS family histone methyltransferase that binds enhancer elements and promotes transcription. KMT2C is mutated in human leukemias, both as part of large deletions of chromosome 7q and at specific domains such as the PHD zinc finger domains (which bind chromatin) or the SET methyltransferase domain (which can prime enhancer elements for activation). Prior murine studies have established that Kmt2c deletions enhance HSC self-renewal and promote leukemogenesis, but the mechanism is not clear. To better understand how Kmt2c regulates HSC self-renewal, we generated germline and conditional loss-of-function mice. Kmt2c deletions enhanced HSC self-renewal, consistent with prior observations, but the mutations did not alter cell cycle kinetics by themselves. Instead, Kmt2c deletions allowed serially transplanted or chemotherapy treated HSCs to retain self-renewal capacity after multiple division cycles. This allowed the mutant HSCs to outcompete wild type HSCs during marrow recovery. In the absence of stress, Kmt2c deletions did not convey a selective advantage. Altogether, our data suggest that Kmt2c mutations mitigate a phenomenon, called HSC exhaustion, in which HSCs lose self-renewal capacity after several cumulative divisions. Our mechanistic data suggest that MLL3 primes HSCs to differentiate in response to IL-1, and possibly other inflammatory cytokines, by either enhancing IL-1 signal transduction or by facilitating IL-1 target gene expression. The aims of this proposal are designed to extend these observations. Aim 1 will test whether Kmt2c/MLL3 deficiency conveys a selective advantage to dividing HSCs by reducing sensitivity to IL-1 and other inflammatory cytokines. Aim 2 will characterize the structure, regulation and IL-1 responsiveness of MLL3 target enhancers in HSCs with short and extensive division histories. Changes in enhancer priming may allow HSCs to archive their division histories and favor commitment, rather than self-renewal, after multiple division cycles. Aim 3 will test whether MLL3 requires functional SET or PHD domains to restrict HSC self-renewal capacity. This structure-function analysis will help us better understand how specific KMT2C mutations might convey a self-renewal advantage. If we can understand how HSCs change as they undergo cumulative self-renewing divisions, and how Kmt2c deletions convey a selective self-renewal advantage, we may ultimately be able to preserve HSC function through periods of stress, such as post-chemotherapy periods, without increasing leukemia risk.

项目概要该提案的目标是了解 KMT2C/MLL3 如何调节造血干细胞 (HSC) 自身更新以及为什么 KMT2C 突变具有可导致白血病的选择性优势。 KMT2C 编码 MLL3 是一种 COMPASS 家族组蛋白甲基转移酶，可结合增强子元件并促进转录。 KMT2C 在人类白血病中发生突变，既是 7q 染色体大缺失的一部分，也是在特定情况下发生的。结构域，例如 PHD 锌指结构域（结合染色质）或 SET 甲基转移酶结构域（它可以启动增强子元件以进行激活）。先前的小鼠研究已证实 Kmt2c 缺失增强HSC自我更新，促进白血病发生，但机制尚不清楚。为了更好地理解为了了解 Kmt2c 如何调节 HSC 自我更新，我们生成了种系小鼠和条件性功能丧失小鼠。公里特2c 缺失增强了 HSC 的自我更新，与之前的观察结果一致，但突变并未改变细胞循环动力学本身。相反，Kmt2c 缺失允许连续移植或化疗治疗 HSC 在多次分裂周期后保留自我更新能力。这使得突变的 HSC 能够在竞争中胜出骨髓恢复期间的野生型 HSC。在没有压力的情况下，Kmt2c 缺失并没有表达选择性优势。总而言之，我们的数据表明 Kmt2c 突变减轻了一种称为 HSC 耗竭的现象，其中HSC在经过几次累积分裂后失去了自我更新能力。我们的机械数据表明 MLL3 通过以下任一方式促使 HSC 响应 IL-1 以及可能的其他炎症细胞因子而分化增强 IL-1 信号转导或促进 IL-1 靶基因表达。该提案的目的是旨在扩展这些观察结果。目标 1 将测试 Kmt2c/MLL3 缺陷是否传达选择性通过降低对 IL-1 和其他炎症细胞因子的敏感性来分裂 HSC。目标2将表征 HSC 中 MLL3 靶增强子的结构、调节和 IL-1 反应性，具有短和广泛的分裂历史。增强子引发的变化可能允许 HSC 存档其分裂历史并在多个分裂周期之后，倾向于承诺，而不是自我更新。目标 3 将测试 MLL3 是否需要功能性 SET 或 PHD 域限制 HSC 自我更新能力。这种结构功能分析将有助于我们更好地了解特定的 KMT2C 突变如何传达自我更新优势。如果我们可以了解 HSC 在经历累积的自我更新分裂时如何变化，以及 Kmt2c 删除如何传达选择性自我更新优势，我们最终可能能够在一段时期内保持 HSC 功能压力，例如化疗后时期，而不增加白血病风险。