Multi-Generational Epigenetic Inheritance and Germline Immortality

描述(申请人提供)：表观遗传学是研究在没有DNA序列相关变化的情况下发生的基因表达或表型的变化。表观遗传过程驱动和/或调节广泛的生物过程，如印记、X染色体失活和参数突变。表观遗传信息可以跨越代际遗传。表观遗传的一个特别显著的例子是dsRNA介导的基因沉默(RNAi)。在线虫基因中，RNAi的作用可以持续十代以上；这一过程被称为RNAi遗传。关于RNAi遗传的下列问题尚未得到回答。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”是如何在几代人之间保持的？在生殖过程中，基因通常受到可遗传的表观遗传调控吗？如果是，原因何在？我们的长期目标是回答这些问题。为了实现这一目标，我们在线虫中进行了基因筛查，旨在确定dsRNA介导的沉默信号遗传所特需的细胞因子。这项筛选鉴定出至少四个基因，其中包括遗传RNAi(Finn)-1失败的基因。Finn-1编码与siRNAs相关的ArgAerte(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与内源性表达的小RNA相关联，这些小RNA指导生殖细胞中染色质的修饰。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丢失，随之而来的是，由于生殖系的多代萎缩，这些动物变得不育。这些结果表明，小RNA与Finn-1共同作用是RNAi遗传和生殖系永生所必需的。在这项提案中，我们试图确定RNAi遗传机制的其他组件，并更详细地探索Finn-1和小调节RNAs如何指导RNAi遗传和生殖系永生。我们的实验正在揭示非编码RNA如何以及为什么驱动表观遗传。非编码RNA与一系列不同的表观遗传现象有关。因此，我们相信，来自我们研究的见解将被证明在全球适用于我们对动物表观遗传遗传的理解。此外，人类表观遗传途径的错误调控也会导致疾病。因此，我们提供的知识可能使影响表观遗传过程以减轻人类疾病的目标成为可能。

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.