Astrocyte-neuron interactions in visual cortex circuits

在初级视皮层（V1），精确的时空神经元反应是已知的基础视觉 处理.虽然神经元在视觉处理中的作用已经得到了很好的研究，但非神经元细胞的作用， 特别是星形胶质细胞在皮层突触和回路中的作用仍然知之甚少。皮质星形胶质细胞接触 并包裹几乎所有的兴奋性突触，产生由突触前输入组成的离散功能单位， 突触后棘和星形胶质细胞突起星形胶质细胞的一个重要功能是主动摄取谷氨酸 从突触间隙通过转运蛋白，特别是GLT 1。我们认为星形胶质细胞从根本上 V1电路通过GLT 1活动，积极塑造突触和神经元的反应概况。局灶性钙瞬变 最近在星形胶质细胞过程中证实了与突触谷氨酸摄取潜在相关， 和突触传递显示积极招募星形胶质细胞GLT 1到突触活性位点。新型高- 分辨率成像技术，以及细胞特异性标记物，新的光学探针， 具有特异性蛋白质表达时间和空间控制的工程小鼠，使我们能够分析 在清醒小鼠体内星形胶质细胞和神经元活动之间前所未有的分辨率串扰。我们的目标是 利用视觉输入到V1神经元的精细组织来检查Ca 2+的相互作用 微结构域，线粒体和谷氨酸转运蛋白在星形胶质细胞的过程中，功能的贡献， 星形胶质细胞转运神经元突触和电路在视觉处理，以及改变的影响， 谷氨酸转运对V1回路发育和可塑性的影响。在目标1中，我们将检查星形胶质细胞 微区Ca 2+对视觉刺激的反应，包括方向特异性光栅和复杂的自然 图像，它们与线粒体的关系，以及GLT 1的遗传或药理学减少如何影响 星形胶质细胞和细胞特异性神经元反应的特异性和可靠性。在目标2中，我们将确定 单树突棘与相邻星形胶质细胞突起之间的功能关系 视觉刺激期间星形胶质细胞和神经元的双波长成像。我们还将确定GLT 1 减少影响星形胶质细胞过程和神经元棘反应和结构。在目标3中，我们将确定 GLT 1在星形胶质细胞反应和视觉皮层回路的发育和可塑性中的作用。我们将 研究GLT 1的生殖细胞减少如何改变正常发育过程中神经元和星形胶质细胞的微结构域反应。 沿着方向选择性的加剧和 双眼定向偏好匹配我们的首要目标是批判性地检验假设， 星形胶质细胞及其转运体是神经元在功能和发育过程中不可或缺的功能伙伴 大脑皮层回路因此，了解正常和异常功能的主机神经发育 和神经退行性疾病将需要结合星形胶质细胞的作用。

In primary visual cortex (V1), precise spatiotemporal neuronal responses are known to underlie visual processing. Though neuronal roles in visual processing have been well studied, the role of non-neuronal cells, particularly astrocytes, in cortical synapses and circuits remains poorly understood. Cortical astrocytes contact and ensheathe nearly all excitatory synapses, creating discrete functional units consisting of a presynaptic input, a postsynaptic spine and an astrocyte process. A crucial function of astrocytes is the active uptake of glutamate from the synaptic cleft via transporters, particularly GLT1. We propose that astrocytes contribute fundamentally to V1 circuits via GLT1 activity, actively shaping synaptic and neuronal response profiles. Focal Ca2+ transients potentially related to synaptic glutamate uptake have recently been demonstrated within astrocyte processes, and synaptic transmission shown to actively recruit astrocytic GLT1 to sites of synaptic activity. Novel high- resolution imaging techniques, together with cell-specific markers, new optical probes, and genetically engineered mice with specific temporal and spatial control of protein expression, enable us to analyze the crosstalk between astrocyte and neuronal activity at unprecedented resolution in awake mice in vivo. We aim to take advantage of the exquisite organization of visual inputs to V1 neurons to examine the interaction of Ca2+ microdomains, mitochondria and glutamate transporters in astrocyte processes, the functional contribution of astrocyte transporters to neuronal synapses and circuits during visual processing, and the impact of altered glutamate transport on the development and plasticity of V1 circuits. In Aim 1, we will examine astrocyte microdomain Ca2+ responses to visual stimuli, including orientation-specific gratings and complex natural images, their relationship to mitochondria, and how genetic or pharmacological reduction of GLT1 impacts the specificity and reliability of astrocyte and cell-specific neuronal responses. In Aim 2, we will determine the functional relationship between single dendritic spines and adjacent astrocytic processes using simultaneous dual-wavelength imaging of astrocytes and neurons during visual stimulation. We will also determine how GLT1 reduction affects astrocytic process and neuronal spine responses and structures. In Aim 3, we will determine the role of GLT1 in the development and plasticity of astrocyte responses and visual cortex circuits. We will examine how germline reduction of GLT1 alters neuronal and astrocyte microdomain responses during normal development and following monocular deprivation, along with the sharpening of orientation selectivity and the binocular matching of orientation preference. Our overarching goal is to critically examine the hypothesis that astrocytes and their transporters are integral functional partners with neurons in the function and development of cortical circuits. As such, an understanding of normal and abnormal function in a host of neurodevelopmental and neurodegenerative disorders will require incorporating the role of astrocytes.