Molecular Genetic Analysis of Extracellular RNAs in C. elegans

描述(申请人提供)：在体液(血清、唾液、母乳等)中发现的胞外RNA。正在作为疾病的敏感序列特异性标记和可能的细胞间信使进行研究。了解特定的RNA是如何被选择和输出的，以及它们是否以及如何被导入到靶细胞中，对于理解它们作为生物标志物、细胞功能的介体和潜在的治疗方法的意义是不可或缺的。在线虫模型系统中发现和鉴定了具有输出和输入双链RNA(DsRNA)沉默信号的RNA转运体，为这一新兴领域提供了分子和遗传方面的见解。在线虫中，引入dsRNA会诱导RNA干扰(RNAi)，这种干扰可以在细胞和组织之间传播。对系统RNAi缺陷(SID)突变体的遗传分析不仅确定了RNA转运蛋白，而且发现了在普遍的细胞生物学过程中发挥作用的调节和生物发生因子，以支持细胞间的RNA运输。SID-1是dsRNA门控的dsRNA特异性通道，负责向细胞提供关键的dsRNA进出口活动。对表达野生型和突变型SID-1蛋白的培养细胞的分析表明，SID-1的核酸运输是dsRNA特异的，对dsRNA的微小化学修饰也很敏感。类似的分析表明，鱼、小鼠和人类的SID-1同源物也运输dsRNA。如果人类同系物对dsRNA具有同样的特异性，并且不能耐受修饰，那么无数旨在稳定血清中治疗性沉默RNA并降低其免疫原性的RNA修饰可能会导致将这些RNA输送到细胞中的困难。在目标1中，我们将确定常见的天然和非天然RNA修饰对线虫和培养细胞中dsRNA转运的影响。这些结果将直接适用于设计有效的人类治疗性siRNA。哺乳动物细胞外RNA通常存在于外体中，即来源于晚期内体/多囊泡体(LE/MVB)的分泌囊泡。SID-5是一种新的LE/MVB相关蛋白，在线虫中是RNA沉默信号有效输出所必需的，这表明外切体可以运输RNA沉默信号。在AIM 2中，我们建议对新的SID蛋白的活性、定位和功能进行表征，包括SID-1和SID-5相互作用蛋白，以深入了解对RNA输出至关重要的生物学过程。这些结果将为外体生物学和细胞外RNA的新兴领域提供遗传学基础和机制理解。在目标3中，我们建议利用Hunter实验室开发的实验专业知识和资源来直接分离内源性胞外RNA，然后使用线虫中成熟的分子遗传学工具来表征它们的表达、运输和功能。了解细胞外RNA信号如何对动物生理起作用，是理解它们作为癌症治疗和其他生物过程的生物标志物和治疗靶点的重要性的关键。

DESCRIPTION (provided by applicant): Extracellular RNAs found in body fluids (serum, saliva, breast milk, etc.) are being investigated as sensitive sequence-specific markers for disease and as possible intercellular messengers. Understanding how specific RNAs are selected and exported and whether and how they are imported into target cells is integral to understanding their significance as biomarkers, as mediators of cellular functions, and as potential therapeutics. The discovery and characterization of RNA transporters that function to export and import double-stranded RNA (dsRNA) silencing signals in the model system C. elegans is providing molecular and genetic insights into this emerging field. In C. elegans, introduced dsRNA induces RNA interference (RNAi) that can spread between cells and tissues. Genetic analysis of systemic RNAi defective (Sid) mutants has identified not only RNA transporters, but regulatory and biogenesis factors that function in universal cell biological processes to support intercellular RNA transport. SID-1, a dsRNA-gated dsRNA-specific channel, confers the key dsRNA import and export activity to cells. Analysis of cultured cells expressing wild-type and mutant SID-1 proteins shows that nucleic acid transport by SID-1 is specific for dsRNA and sensitive to even minor chemical modifications to the dsRNA. Similar assays indicate that fish, mouse, and human SID-1 homologs also transport dsRNA. If the human homologs are equally specific for dsRNA and intolerant to modification, then the myriad of RNA modifications designed to stabilize therapeutic silencing RNAs in sera and reduce their immunogenicity may contribute to the difficulty of delivering these RNAs into cells. In AIM 1 we will determine the effect of common natural and unnatural RNA modifications on dsRNA transport in both C. elegans and cultured cells. These results will be directly applicable to the design of effective human therapeutic siRNAs. Mammalian extracellular RNAs are often found within exosomes, secreted vesicles derived from late endosome/multivesicular bodies (LE/MVB). SID-5 is a novel LE/MVB associated protein required for efficient export of RNA silencing signals, indicating that exosomes may transport RNA silencing signals in C. elegans. In AIM 2 we propose to characterize the activity, localization, and function of new SID proteins, including SID-1 and SID-5 interacting proteins to gain insight into the biological processes important for RNA export. These results will provide a genetic foundation and mechanistic understanding for the emerging fields of exosome biology and extracellular RNAs. In AIM 3 we propose to exploit the experimental expertise and resources developed in the Hunter lab to directly isolate endogenous extracellular RNAs and then to use the well established molecular genetic tools available in C. elegans to characterize their expression, transport, and function. Understanding how extracellular RNA signals contribute to animal physiology is key to understanding their significance as biomarkers and therapeutic targets for cancer therapy and other biological processes.