表观遗传调节子基因UTX与骨髓增生异常综合征的发生

Myelodysplasic syndromes(MDS) comprise a heterogeneous group of acquired clonal hematopoietic disorders. Men have a significantly higher incidence rate than women. Aberrant epigenetic regulation of chromatin plays improtant role in the pathogenesis of MDS. Epigenetic regulator UTX gene locates on the chromosome X and encodes a histone H3 lysine 27 (H3K27) demethylase. UTX escapes X inactivation in females.The Y-linked homologue of UTX, called UTY, does not fully recapitulate the equivalent histone demethylase activity of UTX. Then, loss of function in UTX was significantly more frequent in men than women.Inactivating UTX mutations were found in multiple cancer types recently, defining UTX as a tumor-suppressor gene.However, the role of UTX in pathogenesis of MDS is poorly understood. In this study,we enlarge the cohort enrolled and test bone marrow samples from a panel of patients with MDS, MDS-tAML, with UTX gene mutation analysis and real-time polymerase chain reaction (PCR), integrating clinical and laboratory variables.We analyze the clinical correlation of UTX mutations and the mRNA levels . In vitro, we investigate the effect of overexpression and knock-down of UTX gene on apoptosis, differentiation, and cell number expansion, which is accompanied by changes in cell cycle progression of MDS progenitor cells.We also explore the association between Insulin/IGF-1 signaling pathway targeted by UTX and clinical characteristics to expolore the role of UTX gene in the complex epigenetic pathways and point the new way for MDS therapy.

骨髓增生异常综合征（MDS）是一组异质性克隆性疾患，男性患者居多，表观遗传调节异常是其重要发病机制之一，位于X染色体上的表观遗传调节子基因UTX，逃逸X染色体失活，其主要功能为组蛋白去甲基化酶，同源类似物UTY并不具有同样的酶活性，男性患者可能更易发生UTX表达异常而导致发病性别比例差异。已有研究在多种肿瘤样本中检测到UTX基因失活突变，揭示其为抑癌基因的本质，但UTX在MDS发生发展中的作用机制尚未明确。本研究旨在扩大病例数，检测UTX基因在MDS患者中的突变及表达情况，并分析基因突变类型、表达水平与临床表型、去甲基化药物疗效和预后的相关性，同时进行体外功能实验，进一步阐明UTX 基因异常表达在MDS造血细胞分化受阻、凋亡亢进和生长增殖优势等特征性异常发生中的作用。我们还通过分析UTX基因可能调控的下游Insulin/IGF-1信号途径与MDS患者临床特征相关性，为新的治疗靶点提供线索。

1.位于X染色体上的表观遗传调节子基因UTX，其主要功能为组蛋白去甲基化酶，已有研究在多种肿瘤样本中检测到UTX基因失活突变，揭示其为抑癌基因的本质，但UTX在MDS发生发展中的作用机制尚未明确。在所分析患者中未发现UTX基因突变，在所构建的UTX基因条件性敲除小鼠模型中，长期监测血常规均正常。据此推测仅有UTX基因功能缺失并不能引起血液学异常改变甚至于MDS的发生。.2. HIF1a是与肿瘤发生相关的重要转录因子并且调节免疫细胞激活。我们构建了血液组织特异性（Vav1-Cre）HIF1a转基因小鼠模型（Vav1-Cre/TPM）以证实HIF1a信号通路和MDS发生相关。该小鼠出现全血细胞减少和脾肿大，骨髓多系发育异常。既往文献报导巨噬细胞的某些亚群可参与形成红系造血岛，而HIF1a能激活免疫细胞。Vav1-Cre/TPM小鼠骨髓红系造血岛明显下降，而外周血中单核细胞及Ly6ChighCD8+T细胞增多。CD8+ T细胞IFNg表达增高，这恰与炎症性巨噬细胞增多相关，炎症性巨噬细胞增多而参与红细胞生成的巨噬细胞减少，进而干扰正常的红系造血，引起贫血的发生。.3.内源性和外源性激活EPOR信号通路可引起红系扩增。EPOR信号通路和对红系发生有重要作用的巨噬细胞之间的协同关系仍未知。于是我们分别构建了原发和继发性红细胞增多症模型 (LysM-Cre/Jak2 V617F/+和Alb-Cre/DPM小鼠)，两种模型均发生相同程度的红细胞增多症。前者中红系造血祖细胞在骨髓和脾脏均明显增高，而在后者仅轻度升高。CD169+Vcam1+巨噬细胞在红系造血中发挥重要作用，两种小鼠模型的脾脏中该亚群巨噬细胞比例均明显升高，Alb-Cre/DPM小鼠更为明显。以上发现提示EPOR信号激活不仅可以诱导红系，还有某些巨噬细胞亚群扩增。研究EPOR信号通路诱导巨噬细胞扩增的机制可作为红细胞增多症的治疗靶点。.