Mapping the Inputs onto Neocortical Chandelier Cells

描述(由申请人提供)：GABA能中间神经元在神经元放电和皮层环路整体活动的时空调节中起关键作用。枝形吊灯单元 (CHC)是一类独特的中间神经元，其神经支配具有显著的特点：它们特异性地抑制锥体神经元，特别是在轴突初始段(AIS)--动作电位的产生部位。此外，单个CHC支配皮质中的数百个锥体细胞。因此，CHC准备有力地控制锥体细胞的激活和支持运动和认知功能的整体。对CHC的输入来源和模式的了解是理解CHC如何被招募和调节以在相关的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CHC活动的突触前细胞的位置和身份几乎完全未知。前额叶皮质细胞GABA能标志改变是精神分裂症患者死后脑内最一致的病理改变之一。这些变化被认为是由于输入减少(例如，局部兴奋性驱动或调节通路，但没有提供直接证据)。我的提案AIMS将提供有关CHC输入的第一组数据，并可应用于精神障碍的小鼠模型。因此，我的建议将尝试将局部突触前输入标记到内侧前额叶皮质(MPFC)的第二层(L2)和L5 CCs。我们实验室的初步数据发现，至少有两种CHC亚型仅限于L2和L5。此外，我将标记L2和L5 CHC的长程皮质下和对侧输入。最后，为了评估这种突触前连接是否在大脑各区域之间是保守的，我将标记躯体感觉皮层L2和L5 CHC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，我将使用一种假类型的单突触狂犬病示踪剂，它被证明以一种基于Cre表达的细胞类型特定的方式分离一阶输入。[为了验证到CHC的输入的功能连接，将使用通道视紫红质辅助电路映射(CRACM)来映射对侧皮质、丘脑和神经调制核等区域的远程突触前细胞。]初步数据已经建立了在小白蛋白-Ires-Cre小鼠品系中的狂犬病追踪，以及在转录因子Nkx2.1启动子下的诱导Cre品系。我们发现，在胚胎晚期诱导Nkx2.1-Creer可以标记CHC。该项目将提供关于初级保健中心的第一份投入地图。由于CHC与精神分裂症等精神障碍有关，它们的连通性和功能可能有助于揭示其病理生理学，并提出新的治疗策略。

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.