Molecular and Circuit Mechanisms of Neurexin1-Mediated Goal-Directed Dysfunction

项目摘要 突触黏附分子(SAM)参与神经节细胞的形成、规范和维持。 神经元连接。与神经精神疾病相关的突变的通路分析 突触功能障碍作为一种病理生理机制，使SAMS成为更深层次研究的重要对象 功能探索。对人类的研究表明，神经毒素1α(NRXN1α)是一种突触前定位的 突触结构的组织者，是多发性神经精神疾病的部分穿透性遗传风险因素 疾病表现为目标导向加工的改变。我们证明了NRXN1α突变体表现出很强的健壮性 奖励如何塑造未来选择的变化，可能会提供一个神经电路框架来理解 与许多神经精神障碍相关的僵化和坚持不懈的行为。因此，这项提议 利用遗传、病毒、电生理和行为方法在小鼠中探索NRXN1α是如何 突变会导致神经回路发生变化，从而改变奖赏过程。NRXN1α广泛表达于 大脑，但在皮质和丘脑显示峰值水平，这两个部位的广泛投射到纹状体 规范奖励处理。使用逆行传播的病毒或区域特异性Cre转基因小鼠， 与我们的nrxn1α条件等位基因一起，我们将去除皮层、丘脑或投射神经元中的nrxn1α。 瞄准特定的纹状体隔间。小鼠将在我们的目标导向任务中进行测试，以揭示神经回路 其中，NRXN1α功能障碍会导致奖赏异常。为了阐明这些电路是如何 在NRXN1α突变体中发生生理变化，我们将从电生理学上探索大脑皮质突触强度 以及丘脑对DMS的输入。初步结果提示基础兴奋性突触驱动功能增强 两种DMS棘状神经元亚型。利用光遗传介导的传入招募和场归一化 突触效能测量，我们将确定NRXN1α突变体中输入特异性突触强度的变化。 此外，我们将使用融合通道视紫红质-Cre病毒的稀疏感染进入我们的NRXN1α 条件与急性切片电生理学一起允许选择性地招募NRXN1NRXN1零终端， 从而从机制上洞察由 Nrxn1α功能丧失。仅在NRXN1α突变体中存在电路特异性的生理变化就可以 而不是在功能上牵连到他们的目标导向功能障碍。为了证明这一点，并扩大我们对NRXN1α的分析 中断到电路层面，我们将使用基于病毒的技术进行活动调制，看看是否模仿 野生型小鼠中与NRXN1GDB相关的生理变化可产生突变型α表现或 对抗突变小鼠的这些生理变化是否能抑制突变行为 表型。总之，这项拟议的工作调查了目标导向的神经系统是如何被 突触和回路的变化伴随着NRXN1α的扰动，并可能为 了解奖赏加工中常见的回路变化--这是回路特异性干预的关键一步。

Project Summary Synaptic adhesion molecules (SAMs) are implicated in the formation, specification and maintenance of neuronal connections. Pathway analyses of mutations associated with neuropsychiatric disease implicate synaptic dysfunction as a pathophysiological mechanism, making SAMs important candidates for deeper functional exploration. Studies in humans suggest that Neurexin1α (Nrxn1α), a presynaptically-localized organizer of synaptic architecture, is a partially penetrant genetic risk factor for multiple neuropsychiatric diseases displaying altered goal-directed processing. We demonstrate that Nrxn1α mutants exhibit robust changes in how rewards shape future choices, and may provide a neural circuit framework for understanding inflexible and perseverative actions associated with many neuropsychiatric disorders. This proposal therefore employs genetic, viral, electrophysiological and behavioral approaches in mice to explore how Nrxn1α mutations lead to neural circuit changes capable of altering reward processing. Nrxn1α is widely expressed in brain, but exhibits peak levels throughout cortex and thalamus, sites whose extensive projections to striatum regulate reward processing. Using retrograde-transported viruses or region-specific Cre transgenic mice, together with our Nrxn1α conditional allele, we will ablate Nrxn1α from cortex, thalamus or projection neurons targeting specific striatal compartments. Mice will be tested in our goal-directed tasks to reveal neural circuits wherein Nrxn1α dysfunction precipitates reward abnormalities. To elucidate how these circuits are physiologically altered in Nrxn1α mutants, we will electrophysiologically probe the synaptic strength of cortical and thalamic inputs to the DMS. Preliminary results suggest enhancements in basal excitatory synaptic drive onto both DMS spiny neuron subtypes. Using optogenetic-mediated afferent recruitment and field-normalized synaptic efficacy measures, we will determine input-specific synaptic strength changes in Nrxn1α mutants. Furthermore, we will employ sparse infections of a fused channelrhodopsin-Cre virus into our Nrxn1α conditionals together with acute slice electrophysiology to permit selective recruitment of Nrxn1α-null terminals, thereby gaining mechanistic insight into the cell-autonomous anatomical and synaptic abnormalities caused by Nrxn1α loss-of-function. The mere presence of circuit-specific physiological changes in Nrxn1α mutants does not functionally implicate them in goal-directed dysfunction. To prove this, and broaden our analyses of Nrxn1α disruption to a circuit level, we will use viral-based techniques for activity modulation to see whether mimicking Nrxn1α-associated physiological changes in wildtype mice can produce mutant-like GDB performance or whether counteracting these physiological alterations in mutant mice can suppress the mutant behavioral phenotype. Together, the proposed work investigates how goal-directed neural systems are altered by the synaptic and circuit changes accompanying Nrxn1α perturbation, and may provide a foundation for understanding common circuit changes in reward processing - a key step for circuit-specific intervention.