谷氨酸化修饰调控细胞命运及其机制研究

Cell fate regulation is the result of gene selective expression in a spatial and temporal-specific manner. It is a programmed process accompanied with chromatin structure remodeling, programmed closing and opening of differentiation genes and pluripotent genes. However, it is largely unknown about the regulatory mechanism of cell fate programming and reprogramming. Polyglutamylation modification is involved in multiple life process. But the regulatory role of polyglutamylation in cell reprogramming and early embryonic development has not been reported yet. Our preliminary data show that CCP6 or CCP5 deficiency in mouse embryonic fibroblast (MEF) cells significantly increased the efficiency to form induced pluripotent stem cells (iPSCs).The expression level of TTLL1 (tubulin tyrosine ligase-like enzyme 1) and TTLL4 were upregulated during iPSC induction, while CCP6 (Cytosolic carboxypeptidase 6) and CCP5 were downregulated during this process. Transcriptional factor Sox2 (SRY-box 2) and Klf4 (Kruppel-like transcription factor 4) were identified to be highly polyglutamylated in the process of iPS induction and as substrates for CCP6 and CCP5. Polyglutamylation also occurs in early embryonic development. Based on those results, this study is to take the role and molecular mechanism of Sox2 and Klf4 polyglutamylation in regulating cell fate decision during the process of embryonic development and cell reprogramming, which is to apply early embryonic development, iPS induction and embryonic stem cells as research models. This study is expected to deepen the knowledge to the molecular network in the regulation of cell fate determination.

细胞命运调控是一系列基因时空特异选择性表达的结果，是一种伴随着染色质结构重塑，增殖分化基因及干性基因有序关闭或开放的程序性细胞事件。然而，对调控细胞命运的编程与重编程的机制尚不明了。蛋白质的多聚谷氨酸化修饰调控着多种生命活动，但对细胞重编程及早期胚胎发育的调控作用尚未见报道。我们前期研究发现，CCP6或CCP5基因缺失的MEF细胞，诱导iPS细胞的效率明显提高。TTLL1和TTLL4等在iPS细胞诱导过程中高表达，而CCP6和CCP5等表达下调。我们鉴定发现，Sox2和Klf4在iPS细胞诱导过程中发生高度的谷氨酸化修饰，二者为CCP6和CCP5的作用底物。高度谷氨酸化修饰亦发生在早期胚胎发育过程中。在此基础上，本项目将以早期胚胎细胞增殖分化、iPS细胞诱导体系及胚胎干细胞为模型，研究胚胎增殖分化及重编程过程中，转录因子Sox2和Klf4多聚谷氨酸化修饰调控细胞命运决定的作用及其分子机制。

通过该项目的实施，项目组探究了谷氨酸化修饰调控细胞重编程和早期胚胎细胞增殖分化的调节作用及其机制，以及探究了谷氨酸化修饰调节免疫细胞发育分化及免疫应答调控的作用及机制。主要成果总结如下：1、发现Klf4谷氨酸化修饰促进iPS细胞重编程和调节胚胎早期发育的作用，揭示了谷氨酸化修饰调控细胞命运决定的重要机制；2、发现谷氨酸化修饰参与造血干细胞干性维持的调控及其调节的分子机制；3、揭示了cGAS谷氨酸化修饰参与cGAS活性调控的分子机制；4、发现谷氨酸化修饰调控ILC3细胞的发育分化，阐明了IL-7R谷氨酸化修饰参与ILC3细胞发育分化的分子机制。项目负责人在研究中做出了卓越贡献，以通讯作者发表了高水平的研究论文25篇，包括Cell、Nat Immunol （4篇)、Immunity（2篇)、Nat Cell Biol、Cell Research 、J Exp Med（2篇)、Nat Commun（7篇)、J Hepatol（2篇)等，相关成果申请了3项发明专利。项目负责人获得2018年北京市科技进步一等奖，2019年作为首席科学家获得国家基金委创新群体资助。项目组培养了一批优秀的免疫学研究才俊，4人晋升为教授， 2人获得基金委优秀青年基金资助。综上，本研究得到了全面而深入的探索，完全实现了预期的研究目标。