Mapping the Inputs onto Neocortical Chandelier Cells

描述（由申请人提供）：GABA能中间神经元在皮层回路中神经元放电和整体活动的时空调节中至关重要。枝形细胞 ChC（ChCs）是一类独特的中间神经元，在其神经支配中具有显著特征：它们特异性地抑制锥体神经元，并且特异性地抑制轴突起始段（AIS）-动作电位产生的位点。此外，一个单一的ChC神经支配皮层中的数百个锥体细胞。因此，ChCs准备有力地控制支持运动和认知功能的锥体细胞放电和集合。对ChCs输入的来源和模式的了解是理解它们如何被招募和调节以在相关生理和行为背景下对锥体细胞网络施加强大控制的基础。然而，控制ChCs活性的突触前细胞的位置和身份几乎完全未知。前额叶ChCs中GABA能标记物的改变是精神分裂症患者死后脑组织中最一致的病理学之一。假设这些变化是由于输入减少（例如，局部兴奋性驱动或调节途径）所致，但未提供直接证据。我的提案目标是为ChC提供第一组输入数据，并可应用于精神障碍的小鼠模型。因此，我的建议将尝试标记局部突触前输入到内侧前额叶皮层（mPFC）的第2层（L2）和L5 ChCs。我们实验室的初步数据确定了至少两种局限于L2和L5的ChC亚型。此外，我将标记L2和L5 ChCs的长程皮层下和对侧输入。最后，为了评估这种突触前连接是否在整个大脑区域中保持不变，我将标记躯体感觉皮层中L2和L5 ChCs的本地和远程输入，以与mPFC的数据进行比较。为了实现这些目标，我将采用假型单突触狂犬病示踪剂，已被证明隔离的一阶输入的细胞类型的特定方式的基础上Cre表达。[To为了验证输入到ChC的功能连接性，通道视紫红质辅助回路映射（CRACM）将用于映射对侧皮质、丘脑和神经调节核等区域中的长程突触前细胞。初步数据已经在Parvalbumin-ires- Cre小鼠系和转录因子Nkx2.1启动子下的诱导型Cre系中建立了狂犬病追踪。我们已经发现，在胚胎晚期诱导Nkx2.1-CreER被发现标记ChCs。该项目将首次绘制关于ChCs的投入图。由于ChCs与精神障碍如精神分裂症有关，它们的连接和功能可以揭示病理生理学，并提出新的治疗策略。 公共卫生相关性：精神健康障碍，如精神分裂症、双相情感障碍和自闭症，目前是残疾的主要形式，在美国占总医疗费用的很大比例，每4个美国人中就有1个患有精神障碍。枝形细胞是大脑中强大的抑制性神经元，在精神分裂症中发生改变。这项研究将奠定基础，以确定大脑回路控制吊灯细胞，以进一步了解它们在精神分裂症和其他精神疾病中的变化，这将有望导致新的有效疗法。

DESCRIPTION (provided by applicant): GABAergic interneurons are crucial in the spatial-temporal regulation of neuronal firing and ensemble activity in cortical circuits. Chandelier cells (ChCs) are a unique class of interneuron with striking features in their innervation: they specifically inhibit pyramidal neurons and specifically at axon initial segments (AIS) - the site o action potential generation. Further, a single ChC innervates hundreds of pyramidal cells in cortex. Therefore, ChCs are poised to powerfully control pyramidal cell firing and ensembles that support motor and cognitive functions. Knowledge on the source and pattern of inputs to ChCs is the basis for understanding how they are recruited and regulated to exert powerful control over pyramidal cell networks under relevant physiological and behavioral contexts. However, the location and identity of presynaptic cells that control ChCs activity is almost entirely unknown. Altered GABAergic markers in prefrontal cortex ChCs is one of the most consistent pathology in post mortem brain of schizophrenic patients. These changes are hypothesized to result from reduced inputs (e.g. local excitatory drive or modulatory pathway, but no direct evidence has been provided. My proposal aims will provide the first set of data on inputs to ChCs and can be applied to mouse models of mental disorders. As such, my proposal will attempt to label the local presynaptic inputs to layer 2 (L2) and L5 ChCs in the medial prefrontal cortex (mPFC). Preliminary data from our lab identified at least two subtypes of ChCs confined to L2 and L5. Additionally, I will label the long range subcortical and contralateral inputs to L2 and L5 ChCs. Finally, in order to assess whether this presynaptic connectivity is conserved across brain regions, I will label the local and long range inputs to L2 and L5 ChCs in the somatosensory cortex to compare with the data from mPFC. To accomplish these aims, I will employ a pseudotyped monosynaptic rabies tracer that was shown to isolate the first order inputs in a cell type specific manner based on Cre expression. [To validate the functional connectivity of inputs to ChCs, Channel Rhodopsin Assisted Circuit Mapping (CRACM) will be used to map the long range presynaptic cells in areas such the contralateral cortex, thalamus and neurmodulatory nuclei.] Preliminary data has established rabies tracing in a Parvalbumin-ires- Cre mouse line, and an inducible Cre line under the promoter of transcription factor Nkx2.1. We have found that induction of Nkx2.1-CreER at a late embryonic stage was found to label ChCs. The project will provide the first mapping of input on ChCs. Because ChCs are implicated in mental disorders such as schizophrenia, their connectivity and function could shed light into the pathophysiology and suggest new treatment strategies. PUBLIC HEALTH RELEVANCE: Mental health disorders such as schizophrenia, bipolar disorder and autism are currently the leading form of disability and contribute greatly to total health care costs in the United States with 1 in 4 Americans suffering from mental disorder. Chandelier Cells are types of powerful inhibitory neurons in the brain that are altered in schizophrenia. This research will lay the groundwork to establish what brain circuits control Chandelier Cells in order to further understand how they are changed in schizophrenia and other mental disorders that will hopefully lead to new and effective therapies.