组蛋白精氨酸甲基化调控淋巴细胞分化和白血病发生的表观遗传机制

The methylation of histone arginine residues regulates chromatin structure which controls cell differentiation development with influencing gene expression. The symmetric dimethylation of arginines is catalysed by PRMT5 and PRMT7.Our prelimilary results have shown that expression of PRMT5 and H4R3sme2 modification were upregalted in pediatric acute lymphocyte leukemia, suggestion that PRMT5 and H4R3sme2 might be critical for lymphocyte differentiation and leukemogenesis. In this study, we will further investigate into the molecular mechanism of PRMT5-mediated H4R3sme2 controlling lymphocyte differentiation. ChIP-sequencing and microarray will be used to find out the expression of genes regulated by PRMT5 and H4R3sme2. To determine how PRMT5 was recruited to chromatin in leukemia cells, a protein complex of PRMT5 and binding proteins of H4R3sme2 will be isolated and all components would be identified by proteomics. More importantly, we generated conditional gene knockout mice of PRMT5 and PRMT7. Our prelimilary results have shown that the ratio of hematopoietic stem cells(HSC) and lymphocytic progenitor cells from bone marrow was much higher in PRMT7-/- than that in the WT,suggestion that PRMT7 is an important regulator of cell differentiation in bone marrow.To reveal the function of PRMT5/7 mediated histone modification for blood cell differentiation, the HSC and lymphocytes from WT, PRMT5 cko and PRMT7 cko mice will be analysed through flow cytometry,ChIP-seq, microarray and so on. We believe that the studies proposed in this proposal will reveal the mechanism of PRMT5/7-mediated histone modification in controlling the differentiation of blood cells and leokemogenesis.

组蛋白精氨酸甲基化修饰调控染色质结构，通过调控基因表达控制细胞分化和个体发育。组蛋白对称性甲基化修饰主要由PRMT5和PRMT7催化。本项目在前期发现PRMT5和组蛋白H4R3sme2修饰水平与淋巴细胞分化和儿童白血病发生存在相关性的基础上，利用ChIP-seq、基因芯片、蛋白质复合体分离和质谱分析等手段，进一步研究PRMT5和H4R3sme2调控人淋巴细胞分化的分子机制。我们建立了PRMT5和PRMT7基因条件敲除小鼠，通过流式细胞分析、骨髓细胞移植等手段，研究组蛋白甲基化对造血干细胞和淋巴细胞分化的调控作用；通过ChIP-Seq、基因芯片和蛋白质质谱等技术方法，研究PRMT5、PRMT7和组蛋白精氨酸对称性甲基化修饰对造血干细胞和淋巴细胞分化的调控的作用，揭示染色质结构调控造血细胞分化和白血病发生的分子机制。

在本项目资助下，我们集中研究了组蛋白精氨酸甲基化表观修饰对淋巴细胞命运决定的调控作用，揭示了PRMT5和PRMT7及其催化的H4R3在淋巴B细胞分化和白血病发生中的作用及机制；已发表了3篇SCI研究论文，其中一篇以封面文章发表于国际杂志PNAS，还有1篇论文完成撰写并投稿；培养了3名博士研究生。.成果1：我们构建了PRMT7基因敲除小鼠，发现PRMT7在成熟B细胞向功能浆细胞转化过程中起核心的作用，PRMT7的缺失会导致无功能浆细胞产生，抗体生成缺陷，及脾脏肿大疾病，证明PRMT7和组蛋白H4R3甲基化修饰在成熟B细胞向功能浆细胞转化过程中起核心的作用。相关研究结果于2015年在国际权威免疫学杂志 Journal of Immunology 发表。.成果2：我们研究了PRMT5过量表达可通过甲基化修饰组蛋白H4R3干扰B系细胞正常分化，促进B细胞转化至其前体干性阶段，从而造成肿瘤的发生和恶化的全新机制。相关研究结果已经完成论文撰写并投稿于Leukemia，目前正在审稿中。.成果3：针对儿童白血病临床急需解决的分子分型问题，我们建立了以多点定量PCR为核心的全新白血病诊断分型方法，实现了高准确率，高特异性的白血病分型。这些研究结果以 “An advanced fragment analysis based individualized subtype classification of pediatric acute lymphoblastic leukemia” 为题，发表在Scientific Reports（2015）。.成果4：我们在国际权威科学杂志 PNAS 发表1篇题为 “Loss of the golgin GM130 causes Golgi disruption, Purkinje neuron loss, and ataxia in mice” 的研究论文，并首次报道GM130和高尔基体结构紊乱可直接导致小脑神经元Purkinje细胞死亡和神经退行性疾的发生，证明了高尔基体在神经退行性疾病发生中的作用