Functional organization of neural circuits underlying movement control

描述(申请人提供)：纹状体是基底节的主要输入区，它整合了皮质和丘脑输入传达的感觉和运动信息。该电路的完整性对于各种功能至关重要，包括运动、运动学习和动作选择。目前关于运动指令如何通过基底节回路处理的模型建立在两条互补的通路(直接通路和间接通路)通过特定突触连接的继电器来调节运动控制信息的不同方面的理论基础上。然而，对于直接和间接途径MSN在发育过程中具体的突触连接是如何形成的，几乎一无所知。目前也不清楚与解剖学相关的纹状体神经元是否形成了皮质柱中的功能模块，在皮质柱中，兴奋性皮质神经元的径向克隆优先发展特定的突触连接。基底节神经网络活动障碍导致过多的精神运动障碍，包括帕金森病(PD)、亨廷顿病(HD)和成瘾。多巴胺(DA)是维持正常纹状体功能最重要的神经调节剂之一，帕金森病患者黑质致密部(SNC)多巴胺能神经元的丢失表明，帕金森病患者运动指令的启动和执行严重受损。本研究的长期目标是确定神经回路中特定突触连接功能的调节机制，以及在发育过程中支配突触形成特异性的潜在分子和细胞机制。我目前是哈佛医学院神经生物学系贝尔纳多·萨巴蒂尼博士实验室的博士后研究员。该部门为我提供了一个很好的环境来进行这里提出的研究项目。在这项提议的指导阶段，我们试图解决两个具体的目标：1.表征选择性激活多巴胺轴突后纹状体神经元兴奋性的调节。2.研究纹状核多巴胺能传入对LTS-中间神经元介导的GABA能抑制的调制作用。虽然人们普遍认为DA通过D1受体兴奋直接通路，通过D2受体抑制间接通路，但多巴胺是如何调节不同途径的纹状体功能仍然是个谜。我们的目标是通过结合电生理、成像、光遗传学技术和各种遗传操作来识别纹状体中特定突触连接的特性。在独立阶段，我们的目标是实施我在指导阶段学到的尖端技术，以解决我们对自主运动控制基础功能神经回路的发展和形成的理解中的基本问题。为了解决这些问题，我们提出了具体的目标：3：研究纹状体中特定谷氨酸能突触连接形成的分子机制。4.纹状体基本功能模块的组织特征。拟议的研究将通过相同的电生理学、成像工具和病毒基因操作工具来进行，这些工具适用于转基因BAC小鼠和条件性KO小鼠中已识别的神经元。对这些突触功能的详细电生理学分析以及随后在条件性KO小鼠中对电路功能的表征应该会提供对突触形成调控机制的基本理解，并为理解精细运动控制和动作选择的神经底物提供一个框架。这里提出的研究将提供培训经验，这将是从博士后过渡到独立PI的关键。有了这个拟议的培训计划，我不仅将获得开发实验所需技术的重要培训，而且还将获得在主要研究机构成功运营实验室的管理技能。我一直并将继续与萨巴蒂尼博士就这些目标的各个方面进行讨论，并就拨款的撰写和寻找教职提出建议。 公共卫生意义：帕金森病(PD)是第二种最常见的神经退行性疾病，由黑质致密部的多巴胺能神经缺失引起。在多巴胺丧失后，纹状体神经元突触连接的适应性是显著的，但调控突触形成/维持的分子机制以及多巴胺如何精确地调控纹状体功能仍不清楚。从建议中获得的见解应该为理解精细运动控制和帕金森病发生的病理生理变化的神经底物提供一个框架。

DESCRIPTION (provided by applicant): The striatum is the main input zone of the basal ganglia, which integrates the sensory and motor information conveyed by cortical and thalamic inputs. The integrity of this circuitry is critical for a variety of functions, including locomotion, motor learning and action selection. The current model of how motor command is processed through basal ganglia circuits has been built upon the theory that two complementary pathways (direct and indirect pathways) mediate different aspects of information for motor control through relays of specific synaptic connections. However, virtually nothing is known about how specific synaptic connections are formed during development in direct and indirect pathway MSNs. It is also unclear if anatomically related striatal neurons form functional modules like those seen in cortical columns, where radial clones of excitatory cortical neurons preferentially develop specific synaptic connections. Dysfunction of basal ganglia neural network activity leads to a plethora of psychomotor disorders, including Parkinson's disease (PD), Huntington's disease (HD), and addiction. One of the most indispensable neuromodulators for normal striatal function is dopamine (DA) as suggested by loss of dopaminergic neurons in substantia nigra parc compacta (SNc) in PD, where motor command initiation and execution are severely impaired. The long-term objectives of this study are to define mechanisms that regulate function of the specific synaptic connection in the neural circuit and the underlying molecular and cellular mechanism that governs the specificity of synapse formation during developement. I am currently a postdoctoral fellow at Dr. Bernardo Sabatini laboratory at Department of Neurobiology, Harvard Medical School. The department offers a great environment for me to conduct the research projects proposed here. During mentored phase of this proposal, we try to address two specific aims: 1. To characterize the modulation of neuronal excitability in striatal neurons following selective activation of dopamine axons. 2: To characterize the modulation of LTS-interneuron mediated GABAergic inhibition by dopaminergic afferents in striatal MSNs. Although it is generally accepted that DA acts through D1 receptors to excite the direct pathway and through D2 receptors to inhibit the indirect pathway, precisely how dopamine modulates the different pathway striatal function remains enigmatic. We aim to by using a combination of electrophysiological, imaging, optogenetic techniques and various genetic manipulations to identify properties of specific synaptic connections in the striatum. During the Independent phase, we aim to implement the cutting-edge techniques that I have learned during the mentored phase to tackle fundamental questions in our understanding of development and formation of functional neural circuits underlying voluntary movement control. To address these questions, we propose to address specific aims: 3: To investigate the molecular mechanism governing formation of specific glutamatergic synaptic connectivity in the striatum. 4: To characterize the organization of basic functional modules in the striatum. The proposed studies will be pursued by same set of electrophysiological, imaging tools and viral gene manipulation tools applied to identified neurons either in transgenic BAC mice and conditional KO mice. Detailed electrophysiological analyses of these synapse function and subsequent characterization of the circuit function in conditional KO mice should provide a basic understanding of mechanisms regulating synapse formation and a framework for understanding the neural substrate for fine motor control and action selection. The proposed studies here will provide training experience that will be critical for transition from postdoc to independent PI. With this proposed training plan, I will not only gain important training in developing techniques necessary for experiments, but also managerial skills for running a successful lab at a major research institution. I have been and will continue to discuss with Dr. Sabatini on every aspect of these goals and get advice on grant writing and finding a faculty position. PUBLIC HEALTH RELEVANCE: Parkinson's disease (PD) is the second most common neurodegenerative disorder, which is caused by loss of dopaminergic innervations from the Substantia nigra pars compacta. Following loss of dopamine, the adaptations of synaptic connectivity in striatal neurons are prominent, but molecular mechanisms governing synapse formation/maintenance and how precisely dopamine regulates striatal function remain unclear. The insights gained from the proposed should provide a framework for understanding the neural substrate for fine motor control and pathophysiological changes occurring in PD.