Mechanisms of mRNA localization to neuronal synapses

描述（由申请人提供）：学习和记忆的最佳生物学关联是突触可塑性，或突触数量和强度随经验的变化。长期突触可塑性是一个依赖转录和翻译的过程，可以限制在单个神经元内的突触子集。我们提出一种限制基因表达到单个突触的机制是通过mRNA定位和调控翻译。模型系统为研究突触可塑性提供了一个很好的模型系统。Martin实验室之前的工作已经证明，在培养的海兔感觉运动神经元的学习相关可塑性过程中，蛋白质合成可以在空间上限制于受刺激的突触（Wang et al., 2009）。在这一建议中，我将重点放在编码一种海蛾感觉细胞特异性神经肽，即感觉素的mRNA的突触定位机制上。对神经元和其他非对称细胞类型的研究表明，定位转录本通常在其非翻译区域含有顺式作用的定位元件

DESCRIPTION (provided by applicant): The best biological correlate of learning and memory is synaptic plasticity, or changes in the number and strength of synapses with experience. Long-term synaptic plasticity is a transcription- and translation-dependent process that can be restricted to subsets of synapses within a single neuron. We propose that one mechanism for restricting gene expression to individual synapses is through mRNA localization and regulated translation. The model system Aplysia californica provides an excellent model system to study synaptic plasticity. Previous work in the Martin lab has demonstrated that protein synthesis can be spatially restricted to stimulated synapses during learning- related plasticity of cultured Aplysia sensory-motor neurons (Wang et al., 2009). In this proposal, I focus on the mechanisms underlying the synaptic localization of the mRNA encoding an Aplysia sensory cell-specific neuropeptide, sensorin. Studies in neurons and other asymmetric cell types have shown that localized transcripts often contain cis- acting localization elements in their untranslated regions (UTRs), which often are encoded by stem-loop structures. The Martin lab has demonstrated that the 5' and 3 untranslated regions (UTRs) of sensorin are sufficient for synaptic localization of reporter RNA. While the 3'UTR is required for distal neurite localization, the 5'UTR is required for synaptic localization. I have identified a 66 nucleotide sequence in the 5'UTR of sensorin mRNA that when paired with the sensorin 3'UTR is required and sufficient for sensorin mRNA synaptic localization. My experiments further indicate that this localization element is encoded by a stem-loop structure (Meer et al., 2012). Cis-acting RNA elements interact with trans-acting RNA binding proteins to mediate RNA localization. In addition to characterizing the neuritic RNA localization element in the sensorin 3'UTR, I propose experiments to determine how cis-acting elements function in the RNA stability and translation of sensorin. Finally, I will identify the RN binding proteins that localize sensorin mRNA to neurites and synapses and study the dynamics of these proteins during synapse formation. The results of the proposed experiments will provide insight into the cell and molecular biological mechanisms by which neurons are able to spatially restrict gene expression through mRNA localization and regulated translation. They are of significance to a range of brain disorders in which long-term synaptic plasticity is impaired, including autism, mental retardation, anxiety disorders and drug addiction. PUBLIC HEALTH RELEVANCE: The ability to learn and remember depends on the capacity of connections between nerve cells in the brain to change with experience. Knowledge of the underlying mechanisms that drive such experience-dependent changes in brain circuitry is critical to the development of effective drugs and therapies for a wide range of cognitive disorders, including mental retardation, neuropsychiatric disorders and age-related memory loss.