Temporal dynamics of Arc (Arg3.1) transcriptional regulation

摘要： 学习和记忆缺陷是几种精神疾病的标志， 精神分裂症自闭症和老年痴呆症这些认知过程在正常和疾病中 状态由神经元回路中的时空调控基因控制。研究 暗示了立即早期基因（IEGs）的作用，特别是活性调节的细胞骨架蛋白， 相关（Arc/Arg3.1）的行为反应。Arc引起了人们的特别兴趣，因为它 影响突触传递可塑性和长期记忆从短期的转换 长期记忆，一个被称为巩固的过程，需要Arc蛋白水平 维持数小时至数天。然而，现有的研究表明， Arc mRNA和蛋白质（小于60分钟）。有趣的是，弧的短暂时间窗 在长时间尺度上，表达促进记忆巩固。对于包括Arc在内的IEGs， 基因表达的调节起始于转录水平。因此，我们假设， 在神经元子集中的周期性转录循环将使Arc水平在神经元中持续存在。 稳定记忆痕迹的网络我们建议确定分子机制 这些转录周期的基础。最近，我们建立了一个基因敲入小鼠模型， 当内源性Arc基因用噬菌体衍生的茎环荧光标记时， 能够在单个神经元中实现高检测灵敏度和单个Arc等位基因的成像， 以前所未有的时间分辨率持续数小时通过内源性Arc的实时成像 在培养的神经元和急性海马切片中的基因转录，我们将建立长- Arc转录动力学及其对神经元活动模式的依赖性。我们将 表征活性和翻译反馈在Arc转录调控中的作用， 不同的时间尺度。这将提供对以下内容的深入了解：i）Arc转录调控的长期 影响记忆巩固和ii）改进基于活动的报告器的设计， Arc表达和行为相关。

Abstract: Deficits in learning and memory are hallmarks of several psychiatric disorders including schizophrenia, autism, and Alzheimer’s. These cognitive processes in both normal and disease states are controlled by spatiotemporally regulated genes in neuronal circuits. Studies have implicated the role of immediate-early genes (IEGs), particularly, Activity-regulated cytoskeletal associated (Arc/Arg3.1) in behavioral responses. Arc has garnered special interest because it affects synaptic transmission, plasticity and long-term memory. The conversion from short-term to long-term memory, a process known as consolidation, requires Arc protein levels to be maintained over several hours to days. However, existing studies indicate very short half-lives of Arc mRNA and protein (less than 60 mins). It is intriguing how short temporal window of Arc expression promotes memory consolidation over long time scales. For IEGs including Arc, the regulation of gene expression initiates at the level of transcription. Therefore, we hypothesize that periodic cycles of transcription in a subset of neurons would enable persistence of Arc levels in the network for stabilizing the memory trace. We propose to identify the molecular mechanisms underlying these transcription cycles. Recently, we have generated a knock-in mouse model where the endogenous Arc gene is fluorescently labeled with bacteriophage-derived stem loops, enabling high detection sensitivity and imaging of individual Arc alleles in single neurons over several hours with unprecedented temporal resolution. By real-time imaging of endogenous Arc gene transcription in cultured neurons and in acute hippocampal slices, we will establish the long- term Arc transcription dynamics and its dependence on patterns of neuronal activity. We will characterize the role of activity and translational feedback in Arc transcriptional regulation at different time scales. This will provide insights into: i) how long term Arc transcriptional regulation impacts memory consolidation and ii) improve design of activity-based reporters to reliably correlate Arc expression and behavior.