核基质相关长非编码RNA NMALT1对肝脏脂代谢及三维基因组的调控作用及机制研究

The eukaryotic chromosomes are organized into hierarchical chromatin architectures to coordinate genome functions, yet the underlying mechanisms remain unclear. We hypothesized that Nuclear Matrix-associated RNAs play important roles in the 3D genome organization, and identified 54 Nuclear Matrix Associating Long Transcripts (NMALTs) in the mouse liver. Our preliminary data indicated that NMALT1 is required for the maintenance of the cell identify of hepatocyte. Depletion of NMALT1 resulted in a global condensation of chromatin structure and increases of chromatin interactions between Topologically Associating Domains (TADs). Furthermore, disruption of NMALT1 expression in vivo led to a dysfunction of hepatic lipid metabolism. In this project, we propose to dissect its functions and mechanisms in vivo: 1) to investigate roles of NMALT1 in lipid metabolism in short and long term, through AAV-based RNAi and liver specific knockout, respectively; 2) to analyze targets and regulatory networks of NMALT1 and its roles in 3D genome organization; 3) to explore the association between genetic variant of human NMALT1 and metabolism disorders. These studies may uncover new molecules regulating 3D genome architecture, and may provide potential targets for the etiology, diagnosis and treatment of human metabolism syndromes.

真核细胞中染色体被折叠为不同层级的高级结构来调控基因组功能，但其形成的分子机制依然不清楚。我们假设核基质相关RNA对三维基因组起关键调控作用，并从小鼠肝脏中鉴定出54种核基质相关长非编码RNA（命名为NMALTs）。功能筛查发现：NMALT1为肝细胞特征维持所必需，其缺失会导致染色质结构总体上变浓缩，并导致拓扑关联域（TAD）之间相互作用增加；通过腺相关病毒在小鼠体内干扰NMALT1表达会引发小鼠脂代谢的整体紊乱。本项目拟在前期研究基础上继续探索NMALT1的在体功能及作用机制：1）通过体内RNA干扰及肝脏条件性敲除小鼠分别研究其对脂质代谢的短期及长期影响；2）解析其作用靶点、调控网络以及对染色质三维结构的影响；3）探讨其同源基因的表达及遗传变异与人类代谢综合症的相关性。该项目的研究有可能揭示调控三维基因组构架的新型分子及作用机制，并可为人类代谢综合症的病因分析及诊疗提供新靶点。

核基质是细胞核中的一大类非染色质网状结构，但其生物学功能及作用机制仍不清楚。本项目研究了核基质及其相关非编码RNA对3D基因组及糖脂代谢的调控作用，相关研究成果发表于Molecular Cell, Stem Cell Reports等期刊。主要成果包括：1）发现长非编码RNA lncenc1与核基质蛋白HNRNPK相互作用，通过调控糖酵解通路维持小鼠胚胎干细胞的多能性状态, 其敲除导致成体糖脂代谢平衡的紊乱； 2）发现核基质蛋白SAFB与卫星重复序列转录的RNA相互作用，通过促进相分离来维持近着丝粒异染色的3D结构。此外，我们还发现核基质相关lncRNA NMALT1/linc-Foxa2通过影响核斑完整性来调控3D基因组结构及代谢相关基因表达。这些研究为阐释核基质的功能、3D基因组的调节机制以及糖脂代谢平衡的调控机理提供了科学依据。