Cortico-striatal synaptic defects and compulsive motor behaviors in mice

描述(由申请人提供)：家长奖的中心问题是了解皮质-纹状体突触功能与病理行为之间的关系。要做到这一点，最初的一步是了解SAPAP3基因缺失在小鼠身上造成的纹状体突触缺陷，这种操作产生了一个行为星座(过度梳理、焦虑样行为和氟西汀反应)，表明与强迫症谱系中的人类疾病有关。纹状体在这些行为表现中的中心作用已经通过在体内通过病毒介导的SAPAP3表达专门传递到纹状体来拯救行为而得到证实。由于SAPAP仅在兴奋性突触中检测到，病理性纹状体突触功能的罪魁祸首被进一步缩小。利用全细胞电压钳电生理技术，我们发现了投射到直接和间接通路的中等刺神经元中的兴奋性突触缺陷，以及皮质纹状体和丘脑纹状体回路中的突触。为了最终了解突触缺陷是如何导致行为异常的，了解已定义的突触缺陷如何在电路水平上改变活动是至关重要的。我们建议用实验来补充我们的额外建议，这些实验将采取下一步行动，通过使用新的遗传工具和成像技术来研究SAPAP3功能障碍对纹状体回路的综合影响，这些工具和成像技术在最初提交本奖项时是无法获得的。具体地说，我们建议结合使用表达荧光标记的BAC转基因小鼠识别纹状体细胞类型、检测神经元尖峰的功能成像技术、以不同模式激活传入轴突的常规和光遗传刺激，以及同时对急性脑片中的大量神经元进行成像的先进成像技术，来评估纹状体局部回路中的神经元放电模式。这些技术的综合优势将使我们能够识别SAPAP3 KO小鼠纹状体回路活动的差异，从而克服目前使用传统的急性切片电生理学或活体记录来解决这一问题的不足。我们对孤立的阈值下兴奋性突触缺陷及其对纹状体回路活动的净影响的研究结果将丰富我们对突触功能与行为之间关系的理解，并使可能针对焦点突触机制或其回路扰动的基本疗法的设计成为可能。 公共卫生相关性：SAPAP3功能障碍引起的病理行为可能与涉及强迫行为的人类疾病有关，如强迫症谱系中的那些。在这个小鼠模型中，纹状体功能障碍是行为表达的中心。因此，通过了解纹状体突触传递功能障碍如何导致病理行为，我们的发现也与更广泛的涉及纹状体功能障碍的人类疾病有关，如成瘾、抽动/抽动、帕金森、亨廷顿和肌张力障碍。

DESCRIPTION (provided by applicant): The central question of the parent award is to understand the relationship between cortico-striatal synaptic function and pathological behaviors. The initial step toward this was to understand the striatal synaptic defects created by deletion of the SAPAP3 gene in mice, a manipulation that produced a behavioral constellation (excessive grooming, anxiety-like behaviors, and fluoxetine responsiveness) suggesting relevance to human diseases within the spectrum of Obsessive Compulsive disorders. The central role of the striatum in these behavioral manifestations has been demonstrated by rescuing the behaviors with in vivo viral-mediated SAPAP3 expression delivered exclusively to the striatum. Because SAPAPs have only been detected in excitatory synapses, the culprits of pathological striatal synaptic function were further narrowed down. Using whole-cell, voltage-clamp electrophysiological techniques, we have identified excitatory synaptic defects in medium spiny neurons projecting to the direct and indirect pathways and of synapses in the corticostriatal and thalamostriatal circuits. In order to ultimately understand how synaptic defects produce behavioral abnormalities, an understanding of how the defined synaptic defects alter activity at the circuit level is of paramount importance. We propose to supplement our additional proposal with experiments that take this next step by investigating the integrated effects of SAPAP3 dysfunction on striatal circuitry using novel genetic tools and imaging advances that were not available at the initial submission of this award. Specifically we propose to evaluate neuronal firing patterns in the local circuitry of the striatum by combining the use of BAC transgenic mice expressing fluorescent markers to identify striatal cell types, functional imaging techniques to detect neuronal spiking, conventional and optogenetic stimulation to activate afferent axons in distinct patterns, and advanced imaging techniques to image a large population of neurons in acute brain slices simultaneously. The combined advantages of these techniques will allow us to identify differences in striatal circuit activity in SAPAP3 KO mice in a way that overcomes the current inadequacies of addressing this question using either conventional acute slice electrophysiology or in vivo recordings. The combined result of our investigations of isolated subthreshold excitatory synaptic defects and the net impact on striatal circuit activity will enrich our understanding of the relationship between synaptic function and behavior and enable the design of rationale therapies that may target either focal synaptic mechanisms or their circuit perturbations. PUBLIC HEALTH RELEVANCE: Pathological behaviors due to SAPAP3 dysfunction may have relevance for human disorders involving compulsive behaviors such as those within the spectrum of Obsessive Compulsive disorders. In this mouse model, striatal dysfunction is central to the expression of the behaviors. As such, by understanding how dysfunction of striatal synaptic transmission can lead to pathological behavior, our findings also relate to the broader range of human disorders involving striatal dysfunction, such as addiction, tics/Tourette's, Parkinson's, Huntington's and dystonia.