TET2-mediated transcriptional and epigenetic control of normal and malignant hematopoiesis

TET2介导的正常和恶性造血的转录和表观遗传控制

基本信息

批准号：
10071608
负责人：
Jianlong Wang
金额：
$ 34.06万
依托单位：
UNIVERSITY OF TEXAS HLTH SCIENCE CENTER
依托单位国家：
美国
项目类别：
财政年份：
2019
资助国家：
美国
起止时间：
2019-05-01 至 2023-03-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/10071608
关键词：
TET2 mediated transcriptional epigenetic control

项目摘要

TET2 is one of the most commonly mutated genes in adult myeloid malignancies and in normal individuals over 70 years of age. Tet2-loss leads to increased expansion of hematopoietic stem/progenitor cells (HSPCs) and subsequent development of myeloid malignancies in mice. Thus, TET2 mutations constitute a suitable target for intervention at the early stages of HSPC clonal expansion. To exploit TET2 mutations therapeutically, a better understanding of the mechanisms by which Tet2-loss leads to premalignant HSPC dysregulation and myeloid malignancy development is essential. As a member of the methylcytosine dioxygenase family, TET2 converts 5mC to 5hmC, which can be relatively stable or be further oxidized to 5fC and 5caC. We have reported the requirement of catalytic activity of TET2 in its tumor-suppressive functions in HSPCs. Recently, we identified a novel mechanism of hematological malignancy via the increased mutational burden at genomic sites where TET2 binds and, counterintuitively, with gained 5hmC upon TET2-loss. In addition, we discovered a novel role of TET2 in RNA hydroxymethylation (hm5C) and target transcripts destabilization via its partner and RNA-binding protein (RBP) PSPC1 in mouse embryonic stem cells. Importantly, we found that PSPC1 and its heterodimer partner NONO are both abundantly expressed in HSPCs. Our studies raise two critical questions on TET2 biology in normal and malignant hematopoiesis: 1) How does gained 5hmC contribute to the pathogenesis of myeloid malignancy? 2) Is catalytic activity of TET2 relevant and functional at the RNA hm5C level in HSPCs? We hypothesize that TET2 may exert enzymatic functions through preferential 5hmC- to-5fC/5caC oxidation leading to DNA demethylation and transcriptional activation of tumor suppressor genes and through RNA hm5C modification and consequent destabilization of oncogenic RNAs. We will study how dysregulation of DNA-5hmC and RNA-hm5C mediated epigenetic control upon TET2 mutations can lead to malignant hematopoiesis by three specific aims. Aim 1) Define preferential TET2-mediated 5hmC-5fC/5caC oxidation for DNA demethylation in HSPCs and its dysregulation for the pathogenesis of myeloid malignancy using our newly created 5hmC stalling and catalytically inactive knock-in mutant Tet2 mouse models. Aim 2) Determine the functional significance of the TET2-RUNX1 partnership for TET2 genomic localization and target gene expression in HSPCs. RUNX1, a TET2 binding partner, is reported to be enriched in regions of increased 5hmC, but not in hypo-5hmC regions in TET2 mutant AML. We will study RUNX1 functions in regulating TET2 genomic occupancy in HSPCs and examine the potential role of RUNX1 in imparting unique TET2 functions in preferential 5hmC-to-5fC/5caC oxidation during normal and malignant hematopoiesis. Aim 3) Investigate RBP- mediated TET2 recruitment for RNA hm5C modification and destabilization of oncogenic RNAs in HSPCs and its dysregulation in hematological malignancy. We will also investigate how mutation of TET2 may impair its PSPC1 association in HSPCs leading to malignant hematopoiesis.

TET2 是成人骨髓恶性肿瘤和正常人中最常见的突变基因之一 70岁以上的人。 Tet2 缺失导致造血功能扩张增加干/祖细胞（HSPC）和小鼠骨髓恶性肿瘤的后续发展。因此，TET2突变构成了HSPC早期干预的合适靶点克隆扩增。为了利用 TET2 突变进行治疗，更好地了解 Tet2缺失导致癌前HSPC失调和骨髓恶性肿瘤的机制发展至关重要。作为甲基胞嘧啶双加氧酶家族的成员，TET2 将 5mC 转化为至5hmC，可以相对稳定或进一步氧化为5fC和5caC。我们报道了TET2在其肿瘤抑制功能中的催化活性的要求 HSPC。最近，我们发现了一种通过增加血液恶性肿瘤的新机制 TET2 结合的基因组位点处的突变负担，与直觉相反，增加了 5hmC TET2-损失。此外，我们发现 TET2 在 RNA 羟甲基化 (hm5C) 中的新作用和通过其伴侣和 RNA 结合蛋白 (RBP) PSPC1 在小鼠中破坏目标转录本的稳定性胚胎干细胞。重要的是，我们发现 PSPC1 及其异源二聚体伙伴 NONO 是两者均在 HSPC 中大量表达。我们的研究提出了关于 TET2 的两个关键问题正常和恶性造血的生物学：1) 获得的 5hmC 如何有助于骨髓恶性肿瘤的发病机制？ 2) TET2 的催化活性是否相关且有效？ HSPC 中的 RNA hm5C 水平？我们假设 TET2 可能通过以下方式发挥酶功能： 5hmC 优先氧化为 5fC/5caC，导致 DNA 去甲基化和转录肿瘤抑制基因的激活以及通过RNA hm5C修饰和随后的致癌 RNA 的不稳定。我们将研究 DNA-5hmC 和 RNA-hm5C 的失调如何 TET2 突变介导的表观遗传控制可通过三种方式导致恶性造血具体目标。目标 1) 定义 TET2 介导的 DNA 5hmC-5fC/5caC 优先氧化 HSPC 的去甲基化及其在骨髓恶性肿瘤发病机制中的失调新创建的 5hmC 失速和催化失活敲入突变体 Tet2 小鼠模型。目标2) 确定 TET2-RUNX1 伙伴关系对 TET2 基因组定位的功能意义以及 HSPC 中的靶基因表达。据报道，RUNX1 是一种 TET2 结合伴侣，富含 TET2 突变 AML 中 5hmC 增加的区域，但 5hmC 降低的区域不存在。我们将研究RUNX1 调节 HSPC 中 TET2 基因组占据的功能，并检查 RUNX1 在在正常和正常状态下优先将 5hmC 氧化为 5fC/5caC 时赋予独特的 TET2 功能恶性造血。目标 3) 研究 RBP 介导的 TET2 对 RNA hm5C 的招募 HSPC 中致癌 RNA 的修饰和不稳定及其在血液学中的失调恶性肿瘤。我们还将研究 TET2 的突变如何损害其在 HSPC 中的 PSPC1 关联导致恶性造血。