Multi-Generational Epigenetic Inheritance and Germline Immortality

描述（由申请人提供）：表观遗传学是对在 DNA 序列没有相关变化的情况下发生的基因表达或表型变化的研究。表观遗传过程驱动和/或调节多种生物过程，例如印记、X 染色体失活和副突变。表观遗传信息可以跨代遗传。表观遗传的一个特别引人注目的例子是 dsRNA 介导的基因沉默 (RNAi)。在秀丽隐杆线虫基因中，RNAi的影响可以持续十代以上；这个过程被称为 RNAi 遗传。以下有关 RNAi 遗传的问题尚未得到解答。驱动 RNAi 遗传的分子因子是什么？非编码RNA引导的表观遗传“记忆”是如何跨代维持的？基因在繁殖过程中通常会受到可遗传的表观遗传调控吗？如果是这样，为什么？我们的长期目标是回答这些问题。 为了实现这一目标，我们对秀丽隐杆线虫进行了遗传筛选，旨在识别 dsRNA 介导的沉默信号遗传所需的细胞因子。该筛选鉴定出至少 4 个基因，包括无法遗传 RNAi (finn)-1 的基因。 finn-1 编码与 siRNA 相关的 Argonaute (Ago)，并在暴露于 dsRNA 的动物后代的生殖细胞中促进 RNAi 遗传。在正常生长条件下，FINN-1 与内源表达的小 RNA 结合，指导生殖细胞中的染色质修饰。在缺乏 FINN-1 的动物中，这些染色质标记会随着世代的推移而消失，同时，这些动物会因种系的多代萎缩而变得不育。这些结果证实小RNA与FINN-1联合作用是RNAi遗传和种系永生所必需的。在本提案中，我们寻求确定 RNAi 遗传机制的其他组成部分，并更详细地探索 FINN-1 和小调节 RNA 如何指导 RNAi 遗传和种系永生。 我们的实验揭示了非编码 RNA 如何以及为何驱动表观遗传。非编码 RNA 与多种表观遗传现象相关。因此，我们相信我们的研究成果将在全球范围内适用于我们对动物表观遗传的理解。此外，人类表观遗传途径的错误调节也会导致疾病。因此，我们提供的知识可能会影响表观遗传过程，从而达到减轻人类疾病的目的。

DESCRIPTION (provided by applicant): Epigenetics is the study of changes in gene expression or phenotype that occur without associated changes in DNA sequence. Epigenetic processes drive and/or regulate a wide-variety of biological processes such as imprinting, X-chromosome inactivation, and paramutation. Epigenetic information can be inherited across generational boundaries. A particularly striking example of epigenetic inheritance is dsRNA mediated gene silencing (RNAi). In C. elegans gene the effects of RNAi can persist for more than ten generations; a process termed RNAi inheritance. The following questions concerning RNAi inheritance have not been answered. What is the molecular agent that drives RNAi inheritance? How are non-coding RNA- directed epigenetic "memories" maintained across generations? Are genes normally subjected to heritable epigenetic regulation during reproduction? If so, why? Our long-term goal is to answer these questions. Towards this goal, we have conducted a genetic screen in C. elegans designed to identify cellular factors specifically required for inheritance of dsRNA-mediated silencing signals. This screen identified at least four genes including the gene failure to inherit RNAi (finn)-1. finn-1 encodes an Argonaute (Ago) that associates with siRNAs, and promotes RNAi inheritance, in germ cells of the progeny of animals exposed to dsRNA. Under normal growth conditions, FINN-1 associates with endogenously expressed small RNAs, which direct chromatin modifications in germ cells. In animals lacking FINN-1, these chromatin marks are lost over generations, and, concomitantly, these animals become sterile due to multi-generational atrophy of the germline. These results establish that small RNAs, acting in conjunction with FINN-1, are required for RNAi inheritance and germline immortality. In this proposal, we seek to identify additional components of the RNAi inheritance machinery and explore in more detail how FINN-1 and small regulatory RNAs direct RNAi inheritance and germline immortality. Our experiments are revealing how and why non-coding RNAs drive epigenetic inheritance. Non-coding RNAs are associated with a diverse array of epigenetic phenomena. Therefore, we believe that insights from our research will prove to be globally applicable to our understanding of epigenetic inheritance in animals. In addition, mis-regulation of epigenetic pathways in humans contributes to disease. Thus, the knowledge we provide might make it possible to influence epigenetic processes with the goal of mitigating human disease.