Proliferation, Specification & Brain Function

描述(由申请人提供)：本项目研究在发育中的内侧神经节隆起(MGE)中增殖和神经元间命运决定的相互作用，并探索改变神经元间亚群的功能后果。大脑皮层中几乎所有的神经回路都由谷氨酸兴奋性和GABA能抑制性两大类神经元组成。它们的形态、生化成分、电生理特性和突触连接可以区分不同的中间神经元亚型。尽管这些GABA能细胞对大脑功能很重要，但令人惊讶的是，人们对它们的生产如何在细胞或分子水平上进行调控知之甚少。项目1(Ross Pi)研究了细胞周期成分在哺乳动物大脑的模式和功能中的作用。他们发现，两个Gl期的活性周期蛋白CDI和CD2在MGE的不同祖细胞亚群中表达，其中CD2的遗传消融会导致皮质PV+而不是SST+中间神经元的丢失。实验探讨了CDI主要促进放射状胶质细胞(RGC)不对称分裂的假说，其中一些RGC产生SST+中间神经元。相反，CD2可以促进中间前体细胞(IPC)的对称分裂，这些细胞将主要产生PV+中间神经元。项目2(Anderson Pi)研究了Notch、Wnt和Shh信号系统的相互作用，以调节MGE产生的神经元的数量和亚型。他们发现，Notch信号的调制增强了背侧MGE(DMGE)中CD2的表达，并假设这将以牺牲SST+中间神经元为代价增加PV+输出。试点数据暗示Shh和Wnt信号之间的相互作用调节Notch活性以影响神经元间的产生，这些关系将在项目3(SHPI)中使用最先进的延时视频显微镜和免疫组织化学技术在子宫脑室内注射逆转录病毒荧光蛋白来研究MGE中调节细胞分裂的内在和外部机制。这些研究与项目1和2中的细胞周期和信号研究紧密结合在一起。将确定在该计划内产生的小鼠模型中涉及不同中间神经元亚型和解剖区域的选择性中间神经元缺陷的功能意义。研究了神经元间亚群丢失对行为、脑结构和生理的影响。人们普遍认识到，Notch、Shh和Wnt等关键信号通路和D-Cyclins等细胞周期调节因子广泛相互作用，调节神经元的生成和命运。然而，该区域相互作用的复杂性、腹侧前脑源性神经元命运的多样性以及基因操作的挑战，对MGE的全面研究构成了主要障碍。这个计划通过4个PI的共同努力来解决这个复杂性，使用尖端的方法来阐明发育信号如何调节这些至关重要的神经元的命运和输出。

DESCRIPTION (provided by applicant): This Program examines the interaction of proliferation and interneuron fate determination in the developing medial ganglionic eminence (MGE), and probes functional consequences of altering interneuron subpopulations. Two broad classes of neurons}}}glutamatergic excitatory and GABAergic inhibitory}}} comprise virtually every neural circuit in cerebral cortex. Their morphology, biochemical constituents, electrophysiological properties and synaptic connections can distinguish a remarkable variety of interneuron subtypes. Despite the importance of these GABAergic cells to brain function, surprisingly little is known about how their production is regulated on a cellular or molecular level. Project 1 (Ross PI) studies the roles of cell cycle constituents in the patterning and function of mammalian brain. They found that two Gl-phase active cyclins, cDI and cD2, are expressed in different progenitor subsets in the MGE where genetic ablation of cD2 produces a loss of cortical PV+ but not SST+ interneurons. Experiments probe the hypothesis that cDI functions primarily to promote asymmetric divisions of radial glial cells (RGCs), some of which generate SST+ interneurons. In contrast, cD2 may promote the symmetric divisions of intermediate progenitor cells (IPCs) that will primarily generate PV+ interneurons Project 2 (Anderson PI) investigates the interacting roles of Notch, Wnt and Shh signaling systems to regulate the number and subtypes of neurons generated from the MGE. They have found that modulation of Notch signaling enhances cD2 expression in dorsal MGE (dMGE) and hypothesize that this will increase PV+ output at the expense of SST+ interneurons. Pilot data implicate interactions between Shh and Wnt signaling regulate Notch activity to impact interneuron production and these relationships will be explored Project 3 (Shi PI) uses in utero intraventricular injection of retroviral fluorescent proteins with state-of- the-art time-lapse videomicroscopy and immunohistochemistry to examine cell intrinsic and extrinsic mechanisms regulating divisions in the MGE. These istudies are heavily integrated with cell cycle and signaling investigations in Projects 1 and 2. Core B (Moore Dir.) will determine the functional significance of selective interneuron deficits that involve different interneuron subtypes and anatomical regions in mouse models generated within the Program. Consequences of interneuron subset loss on behavior, brain structure and physiology are sought. It is widely appreciated that key signaling pathways like Notch, Shh, and Wnt and cell cycle regulators like D-cyclins extensively interact to regulate neuronal generation and fate. However the complexity of the interactions, diversity of ventral forebrain-derived neuronal fates and challenges for gene manipulation in this region pose major impediments to comprehensive study in the MGE. This Program tackles this complexity through the combined efforts of 4 Pis using cutting edge approaches to the elucidation of how developmental signals regulate fate and output of these critically important neurons.