Collaborative Research: Ideas Lab: RNA-encoded Molecular Memory (REMM)

在大多数生物体中，遗传信息由脱氧核糖核酸（DNA）分子组成。但是，基因组中只有一小部分DNA--“编码DNA”--包含产生蛋白质的生化指令，这些蛋白质执行生命所必需的广泛活动。事实上，人类基因组的99%被认为是“非编码”DNA。有趣的是，与编码DNA产生的“信使”RNA相反，基因组中这个“非编码”部分的DNA仍然可以产生RNA，尽管这些非编码RNA不会翻译成蛋白质。令人惊讶的是，占基因组很大比例的非编码RNA的功能在很大程度上仍然是未知的。本项目的一个主要目标是探索这些非编码RNA在记忆编码中可能发挥的潜在作用。目前，人们普遍认为记忆是以大脑神经元之间连接强度的变化来存储的。该项目将基于先前的证据，即某些形式的简单记忆可能会被编码为RNA分子的变化。该项目将研究一种简单的记忆形式-行为敏化-是否可以由非编码RNA存储，或者非编码RNA是否可以产生存储记忆的下游分子变化。此外，该项目将加强对未来科学家的培训，包括研究生和博士后研究人员。最后，在STEM中代表性不足的本科生和少数民族学生将在主要研究者的指导下参与拟议的研究，从而更深入地了解科学研究。一位主要研究者（PI）的先前研究表明，长期记忆（LTM）可以通过将受过训练的动物的RNA注射到未经训练的动物中来转移。在这项先前的工作中，从致敏（“训练”）的海生蜗牛（加利福尼亚蜗牛）的神经系统中提取RNA，纯化，然后注射到未经训练的蜗牛中;注射来自训练动物的RNA在未经训练的动物中产生致敏作用，而来自未经训练的供体动物的RNA则不会。PI假设一种或多种非编码RNA（ncRNA）的表达或转录后状态由致敏训练选择性诱导，并且这种分子变化介导了失智症的持续致敏记忆。为了检验这一假设，PI将对来自训练和未训练动物的纯化RNA进行差异RNA-seq，并鉴定具有与LTM显著相关的变化的ncRNA种类。最初的实验将确定特定ncRNA的表达水平是否因致敏而改变。基于这些结果，ncRNA结构，修饰状态或蛋白质相互作用的其他方面将被探索，以探索敏化训练是否诱导这些ncRNA特性的持续变化，这些特性可能介导记忆编码。这项工作将为未来的项目奠定基础，在该项目中，通过用反义寡核苷酸（ASO）破坏候选ncRNA，并评估其对神经元兴奋性和感觉和运动神经元突触连接的影响，以及ASO对完整动物LTM的影响，筛选候选ncRNA的记忆力。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

In most organisms, the genetic information is composed of the molecule deoxyribonucleic acid (DNA). But only a fraction of DNA in the genome—the “coding DNA”—contains biochemical instructions for generating the proteins that perform the vast range of activities essential for life. Indeed, 99% of the human genome is regarded as “non-coding” DNA. Intriguingly, the DNA in this “non-coding” part of the genome can still generate RNA, even though these non-coding RNAs are not translated into proteins, in contrast to the "messenger" RNAs generated by coding DNA. Surprisingly, the functions of non-coding RNAs, which represent a large percentage of the genome, are still largely unknown. A major goal of the present project is to explore potential roles these non-coding RNAs could play in the encoding of memory. At present, memories are widely thought to be stored as changes in the strengths of connections among neurons in the brain. The project will build on prior evidence that some forms of simple memory may instead be encoded as changes in RNA molecules. The project will examine whether one simple form of memory—behavioral sensitization—can be stored by non-coding RNA, or whether non-coding RNA can produce downstream molecular changes that store memory. In addition, the project will enhance the training of future scientists, including graduate students and postdoctoral researchers. Finally, undergraduate and minority students underrepresented in STEM will participate in the proposed research under the mentorship of the principal investigators, and thereby gain a deeper understanding of scientific research.A previous study by one of the principal investigators (PIs) showed that long-term memory (LTM) can be transferred by injecting RNA from trained animals into untrained animals. In this prior work, RNA was extracted from the nervous systems of sensitized (“trained”) marine snails (Aplysia californica), purified, and then injected into untrained snails; injected RNA from trained animals produced sensitization in untrained animals, whereas RNA from untrained donor animals did not. The PIs hypothesize that the expression or post-transcriptional state of one or more non-coding RNAs (ncRNAs) is selectively induced by sensitization training and that this molecular change mediates persistent sensitization memory in Aplysia. To test this hypothesis, the PIs will perform differential RNA-seq on purified RNA from trained and untrained animals and identify species of ncRNA with changes that correlate significantly with LTM. Initial experiments will determine whether the expression levels of specific ncRNAs change as a consequence of sensitization. Based on these results, additional aspects of ncRNA structure, modification state or protein interactions will be probed to explore whether sensitization training induces persistent changes in these ncRNA properties that could mediate memory encoding in Aplysia. This work would set the stage for a future project in which candidate ncRNAs be screened for mnemonic potency by disrupting them with antisense oligonucleotides (ASOs) and assessing the effects on neuronal excitability and synaptic connectivity of Aplysia sensory and motor neurons, as well as the effect of the ASOs on LTM in intact animals.This award was co-funded by the Directorate for Biological Sciences, and the Neural Systems Cluster in the Division of Integrative Organismal Systems.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.