组成型异染色质跨代稳定遗传的分子机制

Genetic information is encoded in the DNA sequences in the genome, and yet the retrieval and interpretation of this information are controlled by epigenetic mechanism, which is the underpinning of the morphological and functional diversity of different cell types seen in one organism. During reproduction, the zygotic genome needs to reset the epigenetic mechanism and remove the constraints in order to regain pluripotency. How is the epigenetic information memorized and subsequently reinstalled during this process is an outstanding question waiting to be fully addressed. We have previously invented a novel sequence-specific DNA visualization method TALE-light, which enables specific labelling of particular genomic locus both live and in fixed tissue samples. Using this method, we studied the emergence of constitutive heterochromatin on different repetitive sequences during Drosophila early embryogenesis, and revealed an unexpected complexity. In particular, we identified a maternally-guided, H3K9me2/3-independent recruiting mechanism of HP1a. Based on these solid preliminary data, in this proposal we want to further interrogate the steps involved in the establishment of different heterochromatic attributes on repetitive sequences, and identify key factors underlying this process. The studies proposed here will uncover how a pivotal epigenetic mechanism—the constitutive heterochromatin—is faithfully transmitted from parents to their offspring during sexual reproduction, and hence provide significant insights into mechanisms of epigenetic inheritance.

遗传信息编码于基因组DNA序列之中，这些信息的读取则由表观遗传学机制所控制。不同的表观遗传学调控决定了不同组织细胞在形态、功能上的多样性。在物种繁衍过程中，表观遗传机制如何在亲代和子代之间准确传递，是一个有待全面研究的重要科学问题。申报人在先前研究中独立发明的TALE-light技术，实现了对基因组中指定DNA序列的实时活体成像及离体标记。利用该技术，申报人在模式生物果蝇中研究了早期胚胎发育阶段重要表观遗传调控机制—组成型异染色质，在基因组中不同重复序列上的建立过程，揭示了其形成过程的多样性，并发现了一种受母体效应调控、不依赖于H3K9me2/3的异染色质蛋白HP1a招募的新途径。基于这些基础，本项目拟解析转录沉默等组成型异染色质的其他特性在发育过程中的建立步骤，并鉴定各特性建立背后的关键因子，从而全面揭示介导组成型异染色质跨代稳定遗传的“表观遗传记忆"的分子机理。

表观遗传调控及其在物种繁衍过程中的跨代遗传机制研究是当前生命科学研究领域的一个重点内容。其中，通过异染色质的形成来选择性沉默基因组中的特定区域是最为重要的一种表观遗传调控机制。立足于项目负责人先前独立发明的TALE-light技术，我们计划解析发育过程中异染色质的转录沉默等特征的建立步骤和关键因素，进而全面揭示介导异染色质跨代稳定遗传的分子机理。.在本项目实施期间，（1）我们首先成功搭建了早期胚胎发育综合型研究平台与基因组学研究平台。（2）随后我们利用活体胚胎荧光成像、高通量测序等方法，发现H3K14ac是一种重要的异染色质跨代遗传标志物，揭示了H3K14ac-SETDB1-H3K9me3调控轴参与组成型异染色质内转座子的转录抑制调控；（3）基于我们建立的基因组学研究平台，我们也通过单胚胎RNA-Seq揭示了提前阻断快速细胞分裂可以触发合子基因组的大规模转录激活，提出了细胞周期重塑调控早期胚胎受精卵基因组转录激活的新理论；（4）联合CHIP-Seq、RNA-Seq等方法，以及我们设计开发的新型O-GlcNAc糖基化荧光探针，我们探究了果蝇胚胎基因组中受O-GlcNAc糖基化修饰和兼性异染色质调控的分子网络；（5）基于我们建立的早期胚胎发育综合型研究平台，我们完成了对有丝分裂检查点复合体核心成分BubR1在调节胰岛素信号通路方面的新功能解析。在本项目的资助下，我们已发表SCI论文3篇，4篇文章撰写投稿中，已申请国家发明专利3项。