Genetic control of chandelier interneuron specification in cerebral cortex

描述（由申请人提供）：大脑皮层内的神经元放电活动由多种抑制性gaba能中间神经元调节，这些中间神经元能够通过大量形态、分子、突触和电生理特性精细地调节回路活动。内在遗传程序和外在经验驱动的学习都可能在定义不同的神经元亚型和将这些细胞以适当的密度分布到整个大脑的层和区域中发挥作用，从而形成有意义的电路基序。为了全面了解中间神经元的发育，下一个挑战是描述真正的中间神经元亚型的整个生活史，如吊灯细胞，可以说是迄今为止最独特和最统一的gaba能中间神经元。吊灯细胞有一个由数百个垂直排列的筒状突触组成的明确轴突轴轴，每个筒状突触都专门支配锥体细胞的轴突初始段，这是动作电位产生的地方。单个枝形细胞可以迅速影响关键皮质层中大量兴奋性细胞的放电，而精神分裂症患者的大脑中出现了枝形细胞钮扣的特异性缺陷，进一步突出了它们的重要性。我们最近表征了小鼠吊灯细胞的时空起源，证明这些细胞起源于与侧脑室相邻的一个以前未被表征的区域，我们称之为腹侧生发区（VGZ）。本研究的目的是发现祖细胞遗传程序和出生时间对大脑皮层关键区域吊灯细胞分布和规格的影响。我们建议将cree依赖性报告因子与发育转录因子的诱导敲入cree驱动因子结合起来，以便在体内发育中的啮齿动物大脑中将吊灯细胞定位到杏仁核、新皮层和海马。此外，我们建议在遗传交叉策略中结合cre和flippase系，以前所未有的时间特异性靶向径向胶质干细胞和中间祖细胞的神经元生成细胞分裂。这些实验将有效地标记出“诞生”时的吊灯细胞，并允许追踪它们进入皮层的轨迹，在那里它们被组装成特定的皮层层。祖细胞分裂的时间和位置在发育过程中被精心安排，这是一个重要的过程，为神经元间锥体细胞突触的形成奠定了基础。理想情况下，这些方法将提供一个无与伦比的例子，说明特定类型的神经元是如何产生的，并适当地分配到皮层中，以整合到神经元回路中。通过研究这些事件，我们希望开始理解神经连接紊乱如何最终表现为精神分裂症的认知和行为障碍，这种疾病折磨着超过1%的普通人群。

DESCRIPTION (provided by applicant): Neuronal firing activity within the cerebral cortex is regulated by a diverse assortment of inhibitory GABAergic interneurons, which are able to finely tune circuit activity through a vast array of morphological, molecular, synaptic, and electrophysiological properties. Intrinsic genetic programs and extrinsic experience- driven learning are both likely to play a role in defining different neuronal subtypes and distributing these cells to layers and regions throughout the brain in the proper density to allow formation of meaningful circuit motifs. To approach a complete understanding of interneuron development, the next challenge is to characterize the entire life history of a bona-fide interneuron subtype such as the chandelier cell, arguably the most distinct and uniform GABAergic interneuron yet to be described. Chandelier cells have an unmistakable axon arbor of hundreds of vertically arranged cartridge synapses, each of which specifically innervates the axon initial segment of a pyramidal cell, the site where action potentials are generated. A single chandelier cell can rapidly impact the firing of large groups of excitatory cells in critical cortical layers, while spcific deficits in chandelier cell boutons occur in the brains of schizophrenia patients, further highlighting their importance. We recently characterized the spatial and temporal origin of chandelier cells in mice, demonstrating that these cells originate in a previously uncharacterized domain bordering the lateral ventricle that we have termed the ventral germinal zone (VGZ). The goal of this proposal is to discover the impact of progenitor cell genetic programs and birth timing on chandelier cell distribution and specification in key regions of the cerebral cortex. We propose to combine cre-dependent reporters with inducible knock-in cre drivers of developmental transcription factors in order to fate map chandelier cells to the amygdala, neocortex, and hippocampus in the developing rodent brain in vivo. Furthermore, we propose to combine cre and flippase lines in genetic intersectional strategies to target neuron-generating cell divisions of radial glial stem cells and intermediate progenitor cells with unprecedented temporal specificity. These experiments will effectively mark chandelier cells at the time of "birth" and allow the tracking of their trajectory into the cortex, where they are assembled into specific cortical layers. The timing and location of progenitor cell divisions are carefully orchestrated during development, an important process that sets the stage for interneuron-pyramidal cell synapse formation. These approaches will ideally provide an unparalleled example of how a specific type of neuron is produced and appropriately dispatched into the cortex for integration into neuronal circuitry. By studying these events, we hope to begin to understand how disordered neuronal connectivity ultimately manifests as debilitating cognitive and behavioral disturbances in schizophrenia, an illness that afflicts more than 1% of the general population.