组织特异性microRNA介导的CUX1转录后沉默及其在发育时序调控中的作用

Recent findings have revealed that miRNAs play critical roles in regulating the timing of embryonic development and cellular differentiation. In the previous study we found that liver-specific miR-122 can directly target and silence the homeobox transcription factor CUX1, cause the transition of hepatocytes from proliferation to differentiation, thereby regulate developmental timing of the liver. Recently, we further find that a large number of tissue-specific miRNA can target CUX1, suggesting that these tissue-specific miRNAs might play a conserved role in timing of cellular differentiation and organogenesis in higher animals, possibly by the post-transcriptional silencing of CUX1. On this basis, we intend to systematically study the expression patterns of miRNAs in several vital organs during mouse development and identify the tissue-specific miRNAs that directly target CUX1 in these tissues. Next, using an integrative approach of experiments and bioinformatics, we will demonstrate the transcription factors that directly transactivate these miRNAs and identify their specific binding sites. Moreover, we will employ several in vitro cell models to study the roles of CUX1 and these tissue-specific miRNAs in the regulation of development and cellular differentiation. The project will demonstrate the role and the discipline of tissue-specific miRNAs in regulating the developmental timing of cellular differentiation and organogenesis, and reveal the intrinsic correlation between the diversity of mammalian cells and the tissue-specificity of miRNAs.

近年研究揭示，miRNA在胚胎发育和细胞分化的时序调控中发挥重要作用。我们前期研究发现，肝脏特异性表达的miR-122可直接靶向并沉默homeobox转录因子CUX1，控制肝脏的发育时序。在此基础上，我们进一步发现，在心肌、神经等细胞中一批组织特异性miRNA可靶向CUX1，提示通过组织特异性miRNA转录后沉默CUX1可能是高等动物细胞分化及器官形成时序调控的一种保守机制。针对这一问题，本项目拟系统研究小鼠器官发育过程中miRNA的时空表达模式，鉴定直接靶向CUX1的组织特异性miRNA，并结合生物信息学和实验方法，系统解析调控这些miRNA的转录因子及其结合位点，最后通过几种体外细胞模型研究特异性miRNA和CUX1对发育分化的作用，藉此阐明组织特异性miRNA在调控器官形成及组织发育时序中的作用及规律，解析哺乳动物细胞多样性和miRNA组织特异性之间的内在联系。

不同的miRNA在胚胎发育和细胞分化的时序调控中发挥不同的作用。本项目发展了一系列的RNA信息学方法，系统研究了小鼠心肌等多种器官发育过程中miRNA的时空表达模式，发现和鉴定miR-208a、miR-192等一批直接靶向homeobox转录因子CUX1的高丰度和组织特异性miRNA，首次揭示了高丰度和组织特异性miRNA 通过抑制转录抑制因子CUX1 调节各种组织细胞终末分化的共同机制，阐明这些miRNA在调控器官形成及组织发育时序中的作用及规律。本研究发现miR-122作为肝脏丰度最高的miRNA, 在决定人类肝细胞终末分化为成熟肝细胞的同时，还能够调控肝细胞天然免疫的新的功能机制。同时，本项目通过对多种细胞体系研究，揭示了高丰度及细胞专一性miRNA调控成肌细胞分化核心信号通路的新机制，以及作为关键分子标志物在肿瘤诊疗及抗癌药物筛选中的应用。