Dissecting the canonical and non-canonical functions of Tet2 in hematopoietic stem cells and hematologic disorders

摘要 骨髓增生异常综合征(MDS)包括一组克隆性血液系统恶性肿瘤，其特征是 无效的造血伴随形态异常，通常仍然是无法治愈的现有的非 移植疗法。Ten-Eleven易位(Tet)蛋白组成一个酶家族，确保 通过DNA去甲基化对基因表达的适当调节，TET2是最常见的 MDS中的突变基因。在基因敲除的小鼠中，大量研究了TET2‘S在造血中的作用；TET2缺失 导致进行性的造血缺陷，包括造血干细胞的异常自我更新 (HSCs)和TET2缺陷小鼠会发展成一种慢性粒-单核细胞白血病样疾病。然而，由于这些 小鼠缺乏完整的蛋白质，目前尚不清楚TET2的非催化功能如何影响HSC功能 以及MDS的发病机制。为了区分TET2的催化和非催化功能，我们有 建立TET2催化失活小鼠。使用这种新的遗传小鼠模型，我们已经获得了 令人信服的证据表明，TET2催化突变小鼠的血液学表型不如TET2明显 基因敲除老鼠。这些初步的发现让我们假设，除了它在DNA中的酶作用之外 羟基化/去甲基化，TET2对于HSCs的正确调控和抑制MDS是至关重要的 不依赖于催化剂的方式。在这项研究中，我们将进行比较表观基因组学，转录和 对TET2催化突变和基因敲除小鼠的血液学分析以确定其非催化需求 TET2在HSC动态平衡和MDS抑制中的作用我们有三个主要目标：(1)确定捐款 非催化TET2对HSC自我更新和分化的作用，(2)确定非催化TET2对HSC的抑制作用 TET2在TET2缺失驱动的MDS中的催化作用，以及(3)识别TET2的非催化靶点 用于抑制异常的HSC动态平衡和MDS的发展。拟议的研究将有一个主要的 通过确定TET2的非催化功能对MDS病因学的贡献，对MDS领域的影响，以及 可以为MDS和其他血液病的治疗和管理带来新的治疗方法 精神错乱。

ABSTRACT Myelodysplastic syndromes (MDS) comprise a group of clonal hematologic malignancies characterized by ineffective hematopoiesis coupled with morphologic dysplasia, and generally remains incurable by existing non- transplant therapy. The Ten-eleven translocation (TET) proteins constitute a family of enzymes that assure proper regulation of gene expression through DNA demethylation, and TET2 is one of the most frequently mutated genes in MDS. Tet2’s roles in hematopoiesis have largely been studied in knockout mice; Tet2 deletion causes progressive defects in hematopoiesis, including the aberrant self-renewal of hematopoietic stem cells (HSCs), and Tet2-deficient mice develop a chronic myelomonocytic leukemia-like disease. However, as these mice lack the entire protein, it is not known how the non-catalytic functions of Tet2 contribute to HSC function and MDS pathogenesis. In order to delineate the catalytic and non-catalytic functions of Tet2, we have established Tet2 catalytically inactive mice. Using this new genetic mouse model, we have obtained the compelling evidence that Tet2 catalytic mutant mice have less pronounced hematologic phenotypes than Tet2 knockout mice. These preliminary findings led us to hypothesize that, in addition to its enzymatic roles in DNA hydroxylation/demethylation, Tet2 is critical for the proper governance of HSCs and suppression of MDS in a catalytic-independent manner. In this study, we will conduct a comparative epigenomic, transcriptomic and hematologic analyses of Tet2 catalytic mutant and knockout mice to establish the non-catalytic requirements of Tet2 in HSC homeostasis and MDS suppression. We have three main goals: (1) to determine the contributions of non-catalytic Tet2 functions to HSC self-renewal and differentiation, (2) to define the suppressive roles of non- catalytic functions of Tet2 in loss-of-Tet2-driven MDS, and (3) to identify non-catalytic targets of Tet2 responsible for suppressing aberrant HSC homeostasis and MDS development. The proposed research will have a major impact on the MDS field by defining the contribution of the non-catalytic functions of TET2 to MDS etiology, and can lead to new therapeutic approaches for the treatment and management of MDS and other hematologic disorders.