甲基化敏感的增强子元件DERARE在造血调控和白血病克隆演变中的作用和机制研究

As one of the major epigenetic marks, DNA methylation dictates spatial and temporal gene expression in stem cells and their progeny and plays fundamental roles in multiple biological processes, such as embryonic development, stem cell regulation, X-chromosome inactivation and genomic imprinting. Aberrant DNA methylation and mutations in DNA methyltransferase and methylcytosine dioxygenase enzymes, such as Dnmt3a and Tet2, have been frequently found in multiple types of cancer including leukemia. Although advanced technologies of genome-wide methylome sequencing have identified thousands of differentially methylated regions (DMRs) on cis-regulatory modules, much remains unknown about the physiological functions and underlying mechanisms of individual DMR in stem cell differentiation and cancer development. Our recent studies have demonstrated the critical roles of two imprinting DMRs, H19-DMR and IG-DMR, in maintaining quiescent and low metabolic states of LT-HSCs. To systematically identify DMRs during HSC differentiation, we have performed whole genome bisulfite sequencing in four adult HSC populations and found thousands of DMRs from pairwise comparison analyses. In combination with our transcriptome data, we identified a HSC-specific DMR, DERARE, within the HoxB cluster. Our observations that homozygous deletion of DERARE dramatically reduced absolute number of LT-HSCs, and markedly diminished expression of HoxB cluster genes and H3K27ac activity on the DERARE, led us to our central hypothesis that DERARE functions as a methylation-sensitive enhancer to orchestrate expression of HoxB cluster genes in both normal hematopoiesis and leukemogenesis. These studies will enable us to gain insight into the mechanisms by which DERARE orchestrates HoxB cluster expression in normal hematopoiesis and leukemogenesis. Additionally, the proposed experiments will permit the development of specific pharmaceuticals that can be used for the treatment of leukemia with aberrant methylation of DERARE and overexpression of HoxB genes.

DNA甲基化作为主要表观因子，在胚胎发育、干性维持、X染色体失活、基因印记中起重要作用。在白血病中经常出现甲基化异常和甲基化酶突变。虽然新一代甲基化测序发现很多差异甲基化区域（DMR）位于顺式作用元件，但每个DMR在造血调控和癌症中的功能和机制尚不清楚。我们前期报道两个印记基因簇控制区H19-DMR和IG-DMR，对维持HSC静息和低代谢的状态十分重要。为了系统性筛选DMR，我们在HSC中开展甲基化测序并鉴定出上千个DMR。转录本测序鉴定出位于Hoxb聚簇的HSC特异的DMR—DERARE。预期实验观察到DERARE敲除的HSC中，HSC减少，DERARE增强子活性和Hoxb表达显著下降。因此我们推测: DERARE作为控制Hoxb聚簇的甲基化敏感的增强子元件，在造血调控和白血病克隆演变中起重要作用。本课题将揭示DERARE在造血调控和白血病克隆演变中的功能和机制，为新型药物开发提供思路。

DNA甲基化作为主要表观因子，在胚胎发育、干性维持、X染色体失活、基因印记中起重要作用。在白血病中经常出现甲基化异常和甲基化酶突变。虽然新一代甲基化测序发现很多差异甲基化区域（DMR）位于顺式作用元件，但每个DMR在造血调控和癌症中的功能和机制尚不清楚。我们前期报道两个印记基因簇控制区H19-DMR和IG-DMR，对维持HSC静息和低代谢的状态十分重要。为了系统性筛选DMR，我们在HSC中开展甲基化测序并鉴定出上千个DMR。转录本测序鉴定出位于Hoxb聚簇的HSC特异的DMR—DERARE。预期实验观察到DERARE敲除的HSC中，HSC减少，DERARE增强子活性和Hoxb表达显著下降。在本项目中，我们明确DERARE元件对AML细胞的增殖、凋亡、分化等功能的作用和机制，阐明白血病特异DERARE元件在AML发生发展过程中的上下游分子调控机制，分析DERARE元件甲基化和AML病人病理指标和预后之间的相关性，为防治AML和开发新型基因治疗药物提供新思路和新靶点。本研究的实施将使我国在差异甲基化区域和造血调控的研究领域保持领先，并可望为DNMT3A突变的AML的治疗提供新的基因治疗策略。此外，在项目执行期间，共计发表SCI论文8篇，获得国家自然科学基金优青项目1项和国家发明型专利授权2项，参加国际学术会议及国内学术会议各一次，培养博士毕业生1名、硕士毕业生2名，圆满完成项目申请书中的各项预期指标。