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受多种抑制性GABA能中间神经元的调节，这些中间神经元能够通过大量的形态学、分子、突触和电生理学特性精细地调节回路活动。内在的遗传程序和外在的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以允许形成有意义的电路基序方面发挥作用。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，例如枝形细胞，可以说是迄今为止描述的最独特和最均匀的GABA能中间神经元。枝形细胞有一个明确无误的轴突乔木数百垂直排列的盒式突触，其中每一个专门支配的轴突起始段的锥体细胞，在那里产生动作电位。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枝形细胞钮的特异性缺陷，进一步突出了它们的重要性。最近，我们的特点是在小鼠的吊灯细胞的空间和时间的起源，表明这些细胞起源于一个以前未知的域接壤的侧脑室，我们称之为腹生发区（VGZ）。这项计划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枝形细胞分布和规格的影响。我们建议将联合收割机依赖cre的报告基因与发育转录因子的可诱导敲入cre驱动基因相结合，以便在体内发育中的啮齿动物大脑中将枝形细胞命运映射到杏仁核、新皮质和海马。此外，我们建议将联合收割机cre和翻转酶系在遗传交叉策略中以前所未有的时间特异性靶向放射状胶质干细胞和中间祖细胞的神经元生成细胞分裂。这些实验将在“出生”时有效地标记吊灯细胞，并允许跟踪它们进入皮质的轨迹，在那里它们被组装成特定的皮质层。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。这些方法将理想地提供一个无与伦比的例子，说明一种特定类型的神经元是如何产生的，并适当地被分派到皮层中，以整合到神经元回路中。通过研究这些事件，我们希望开始了解神经元连接紊乱最终是如何表现为精神分裂症患者的认知和行为障碍的，精神分裂症是一种折磨超过1%的普通人群的疾病。

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.