Role of lincRNAs in HSC function and leukemogenesis

摘要 HOX基因，特别是HOXA和HOXB基因，对于维持自我更新之间的平衡至关重要 造血干细胞(HSCs)的分化。HOXA和/或HOXB基因的失调是一种 白血病转化的主导机制。HOX基因异常表达与融合相关 涉及MLL1和NUP98的基因以及NPM1和CEBPA的突变。然而，表观遗传机制 如何通过调控HOX基因转录来调控HSC的功能仍有待探索。此外，至关重要的是 阐明HOX基因在白血病发生过程中如何异常激活。更好地理解这些 关键问题将有助于开发高效和选择性的靶向治疗。我们最近 发现了一个与HoxB基因座相关的长基因间非编码RNA(LncRNA)，HoxBlinc，它控制 CTCF介导的活性染色质结构域介导的造血祖细胞定向和分化 以促进前路HoxB基因的激活。HoxBlinc招募SETD1A/MLL1复合体激活HoxB 基因。我们发现HoxBlinc lncRNA在很大一部分AML患者中过表达，AML 与HoxBlinc低表达患者相比，HoxBlinc高表达患者的生存期显著缩短 HOCBLINC表达式。此外，在小鼠中转基因表达HoxBlinc会导致更多的 LT-HSCs和ST-HSCs，以及致命性AML样病的发生。我们假设HoxBlinc lncRNA是 HSC的关键表观遗传调节因子，通过控制HOX和其他关键的HSC调节基因的激活 通过对染色质动力学的调节。此外，上调HoxBlinc可能代表着一种强有力的 白血病发生中的致癌事件。为了检验这些假设，我们将：1)确定HoxBlinc的作用 通过进行连续移植和配对子细胞检测研究肝干细胞生物学和行为中的lncRNA 使用纯化的HoxBlinc-TG HSCs；2)确定转基因HoxBlinc的表达是否足以干扰 造血与导致小鼠髓系恶性肿瘤；3)探讨荷瘤小鼠的致盲机制(S) IncRNA通过检测HoxBlinc染色质的全局变化来调节不同阶段的HSCs的行为 结合、3D染色质组织、组蛋白修饰、染色质可及性以及转录 WT和HoxBlinc-TG小鼠纯化的HSCs的特征；4)检测HoxBlinc是否发挥作用 HSCs中的lncRNA依赖于SETD1A/MLL1复合体；5)探索HOXBLINC lncRNA是否可以 通过检查HoxBlinc丢失是否能够缓解AML，作为AMLS的有效治疗靶点 NPM1C或其他突变驱动的髓系恶性肿瘤--通过取消标志性异常HOX基因 表情。拟议研究的成功将带来有关监管的基本知识 通过InncRNAs诱导的HSCs。我们的研究可以确定HoxBlinc是一种强大的致癌基因 白血病的发生。HOXBLINC lncRNA可能是治疗高血压性急性髓系白血病的新靶点 HOXBLINC表达式。

Abstract Hox genes, especially HOXA and HOXB genes, are critical for maintaining the balance between self-renewal and differentiation of hematopoietic stem cells (HSCs). Dysregulation of HOXA and/or HOXB genes is a dominant mechanism of leukemic transformation. Aberrant HOX gene expression is associated with fusion genes involving MLL1 and NUP98, and mutations in NPM1 and CEBPA. However, the epigenetic mechanisms that regulate HOX gene transcription to control HSC function remain to be explored. Furthermore, it is critical to elucidate how HOX genes are aberrantly activated during leukemogenesis. Better understanding of these critical questions will assist in the development of highly effective and selective targeted therapies. We recently identified a HoxB locus associated long intergenic noncoding RNA (lncRNA), HoxBlinc, which controls hematopoietic lineage commitment and differentiation by organizing CTCF mediated active chromatin domain to facilitate anterior HoxB gene activation. HoxBlinc recruits the Setd1a/MLL1 complexes to activate HoxB genes. We found that HoxBlinc lncRNA is overexpressed in significant portions of AML patients, and AML patients with high HoxBlinc expression had significantly shortened survival compare to patients with low HOCBLINC expression. Furthermore, transgenic expression of HoxBlinc in mice leads to increased pools of LT-HSCs and ST-HSCs, and development of lethal AML-like disease. We hypothesize that HoxBlinc lncRNA is a critical epigenetic regulator of HSCs, by controlling the activation of Hox and other key HSC-regulating genes through modulation of chromatin dynamics. In addition, up-regulation of HoxBlinc may represent a potent oncogenic event in leukemogenesis. To test these hypothesis, we will: 1) determine the role of HoxBlinc lncRNA in HSC biology and behavior by performing serial transplantation and paired daughter cell assays using purified HoxBlinc-Tg HSCs; 2) determine whether transgenic HoxBlinc expression is sufficient to perturb hematopoiesis and cause myeloid malignancies in mice; 3) investigate the mechanism(s) by which HoxBlinc lncRNA regulates behaviors of different stages of HSCs by examining global changes in HoxBlinc chromatin binding, 3D chromatin organization, histone modifications, chromatin accessibility, as well as transcription profiles in HSCs purified from WT and HoxBlinc-Tg mice; 4) examine if the function exerted by HoxBlinc lncRNA in HSCs is dependent on the Setd1a/MLL1 complexes; 5) explore whether HOXBLINC lncRNA can serve as an effective therapeutic target for AMLs by examining whether HoxBlinc loss is capable of mitigating NPM1C+- or other mutation-driven myeloid malignancies via abrogating the signature aberrant HOX gene expression. Success of the proposed studies will result in fundamental knowledge regarding the regulation of HSCs by lncRNAs. Our studies could establish HoxBlinc as a powerful oncogenic lncRNAs during leukemogenesis. HOXBLINC lncRNA might represent a novel therapeutic target for AMLs with high HOXBLINC expression.