基因组稳定性的节律性调控与肝脏衰老研究

Aged people usually suffer circadian degeneration. Clock dysfunction could lead to premature aging, but the underlying mechanism remains largely unknown. Genomic instability and aging have a reciprocal causation. Our previous data showed core clock control gene Bmal1 dramatically downregulated in aged liver. Bmal1 depletion induced DNA damage accumulation and dysregulation of Pentose Phosphatase Pathway in mouse liver. Moreover, Bmal1 directly involved in DNA damage response. In this project, we will employ several mouse models, including ATM-deficient, Bmal1-stopFL and Bmal1-stopFL/Alfp-cre mice, to screen the Bmal1-controlled and aging-related genes or metabolic pathway involving in DNA repair, based on the combined big-data analysis of transcriptome, metabolome, and ChIP-seq. We also will use comet assay and I-Scel/DR-GFP HR reporter to figure out the correlation between circadian dysfunction and genomic instability. In order to measure the beneficial effect of improving genomic stability on the healthspan of Bmal1-deficent mice, we will administrate these mice with dietary supplementation or low dose of chloroquine. These studies will not only uncover the novel mechanism of genomic stability, but also expand the physiological function of circadian clock, providing the new molecular targets and therapy strategies for anti-aging and preventing aging-related diseases.

生物钟退化是老年人常见症状，节律钟紊乱往往导致过早衰老，但关联机制并不清楚。基因组不稳定性是衰老的内在推动力。我们初步研究发现，节律核心元件Bmal1缺失的早老小鼠肝脏中DNA损伤累积、戊糖磷酸途径失调；该基因表达在老年肝脏中显著下调；Bmal1蛋白参与DNA损伤应答ATM活化。本项目将以ATM基因敲除、Bmal1基因敲除及肝脏特异性回补等小鼠模型，采用多组学整合分析（转录组、代谢组和ChIP-seq），筛选Bmal1调控、衰老有关、参与DNA损伤修复通路的相关基因或代谢途径；利用彗星实验和Ⅰ-Sce I/DR-GFP同源修复报告系统等手段，阐明节律钟紊乱与基因组不稳定性的关联机制；通过膳食添加或氯喹喂食，探讨增强基因组稳定性对Bmal1缺失早老小鼠健康寿命的影响。该预期成果将揭示基因组稳定性调控的新机制，拓展节律钟的生理功能，为人类研发抗衰老及干预衰老相关疾病提供新的药物靶点和治疗策略。

生物钟紊乱与代谢失衡及器官衰老密切相关。肝脏是机体重要代谢器官，具有外周自主节律钟。肝脏节律钟失衡如何导致肝脏功能障碍和衰老的分子机理还不清楚。本课题旨在从基因组稳态视角探究节律钟对肝脏功能稳态调控的作用。在本项目的资助下，我们围绕 “节律钟核心元件Bmal1如何调控肝脏基因组稳定性与衰老”展开研究，取得了多项成果。. 通过代谢组学分析发现肝脏磷酸戊糖途径（PPP）存在明显外周节律性，而在饮食颠倒或Bmal1缺失肝脏中PPP代谢产物节律性丧失。C13标记的代谢流显示在Bmal1缺失细胞中PPP代谢率下降。在全身敲除的Bmal1小鼠肝脏特异性回补Bmal1能够挽救G6PD的转录水平和振荡规律，进而确证PPP代谢的属于肝脏外周自主节律。进一步研究证实Bmal1协同氧诱导因子-1（HIF1a）调节PPP关键限速酶G6PD的振荡表达。由于PPP代谢产物是细胞维持氧化还原态和核苷酸生物合成的重要基础，我们发现Bmal1缺失肝脏中核苷酸合成的昼夜节律变化消失，肝脏再生能力显著下降；肝脏细胞氧化损伤明显，基因组DNA损伤累积，进而致使细胞衰老。. 因此，本项目揭示了肝脏自主生物钟通过磷酸戊糖代谢调控基因组稳定性从而维持和保障了肝脏功能稳态和再生能力的分子机理，进而阐明节律钟对器官功能稳态的重要作用。本项目研究成果联系起节律-代谢-基因组稳态的调控信号轴，为理解和干预器官衰老提供重要基础。