Investigation of experience-dependent post transcriptional regulation of Drosophi

描述（由申请人提供）：虽然大量的经验产生短暂的记忆，只有其中一些形成稳定的长期记忆。经验的价值和有机体的内部状态在决定这种从短期记忆到长期记忆的转变中起着重要的作用。然而，外部经验和有机体的内部状态如何在分子水平上相互作用以影响记忆储存， 未知新蛋白质的合成是形成稳定的长期记忆所必需的。CPEB是RNA结合蛋白家族，调节神经元中活性依赖性蛋白质合成。在失智症中，一种特定的CPEB家族成员ApCPEB是突触强度持续增加超过24小时所必需的。在果蝇中，CPEB家族成员Orb 2需要稳定记忆超过12小时。在小鼠和人类中，CPEB家族成员CPEB 3与情景记忆形成有关。这些观察结果表明，CPEB家族成员在记忆的持久性中发挥着进化保守的作用。果蝇Orb 2基因从两个不同的转录起始位点产生两种不同的初级转录物，编码Orb 2A和Orb 2B蛋白。选择性破坏Orb 2A蛋白的突变会使长期记忆不稳定。我们已经发现Orb 2A mRNA有两种形式：一种是包含不编码Orb 2A蛋白的未剪接形式（Orb 2A-np）的内含子，另一种是编码全长Orb 2A蛋白的剪接形式（Orb 2A-pc）。令人惊讶的是，Orb 2A-np mRNA是成人大脑中普遍存在的同种型，并且暴露于在果蝇中形成关联长期记忆的线索，例如将饥饿的果蝇暴露于蔗糖和气味，增加了编码剪接的Orb 2A-pc转录物的蛋白质的水平。哺乳动物剪接调节因子Nova的果蝇同源基因结合Orb 2A转录本并调节Orb 2A-pc mRNA的形成。本研究拟从行为线索和Nova依赖性分子机制两个方面对Orb 2A转录水平的调控机制进行深入研究。我们还打算解决何时以及多久需要Orb 2蛋白的记忆持久性。我们希望了解经验和稳定记忆的分子之间的相互作用，将有助于理解成瘾和创伤后综合征，其中单一的经验形成非常稳定的记忆。此外，我们希望深入了解调节mRNA加工在持久记忆中的作用。

DESCRIPTION (provided by applicant): Although a large number of experiences produce transient memory only some of them form stable long-term memory. The value of the experience and internal state of the organism plays an important role in determining this transition from short-term to long-term memory. However, how external experience and the internal state of the organism interact at a molecular level to influence memory storage is largely unknown. The synthesis of new proteins is required to form stable long-term memory. CPEB, a family of RNA-binding proteins, regulate activity-dependent protein synthesis in the neuron. In Aplysia, a specific CPEB family member, ApCPEB, is required for the persistence of activity-dependent increase in synaptic strength beyond 24 hours. In Drosophila, a CPEB family member Orb2 is required to stabilize memory beyond 12 hours. In mice and human a CPEB family member CPEB3 has been linked to episodic memory formation. These observations suggest that CPEB family members play evolutionarily conserved role in the persistence of memory. The Drosophila Orb2 gene produces two distinct primary transcripts from two different transcription start sites, encoding the Orb2A and Orb2B proteins. Mutations that selectively inactivate Orb2A protein specifically destabilize long-term memory. We have found that the Orb2A mRNA has two forms; an intron containing unspliced form that does not code for Orb2A protein (Orb2A-np) and a spliced form that codes for full length Orb2A protein (Orb2A-pc). Surprisingly, the Orb2A-np mRNA is the prevalent isoform in the adult brain and exposure to cues that form associative long-term memory in flies, such as exposure of hungry flies to sucrose and odor increases the level of protein coding spliced Orb2A-pc transcript. The Drosophila orthologue of mammalian splicing regulator Nova binds Orb2A transcript and regulates the formation of Orb2A-pc mRNA. In this proposal we intend to dissect the behavioral cues and Nova-dependent molecular mechanism that regulate the level of protein coding Orb2A transcript. We also intend to address when and how long Orb2 proteins are required for persistence of memory. We hope that an understanding of the interaction of experiences and molecules that stabilize memory would be useful to understand addictions and post traumatic syndromes, in which a single experience forms extremely stable memory. Also, we hope to gain insight into the role of regulated mRNA processing in long-lasting memory.