Intercellular Communication in Retinal Development

描述（由申请人提供）：神经元的输出不仅受兴奋的影响，还受神经递质γ-氨基丁酸（GABA）和甘氨酸介导的抑制的幅度和时间的影响。当兴奋不能被抑制适当地控制时，神经回路就变得功能失调，这在许多神经系统疾病中都有发现。我们对组装和维持适当抑制连接的细胞相互作用的理解远远落后于我们对兴奋回路的了解。在这个项目中，我们建议显着推进知识的发展和功能维护的抑制连接，控制兴奋性神经递质从轴突的释放。我们将集中在视网膜双极细胞轴突末端的抑制性突触。这些神经元对于将视觉信号从光感受器传递到视网膜神经节细胞是必不可少的。从这些细胞的传输是由至少两种不同类型的抑制性突触。在目标1中，我们将遗传标记离子型GABAA和GABAC受体，其调节对相同轴突的抑制，但具有不同的动力学。我们将使用相关的荧光成像和连续块面扫描电子显微镜映射不同类型的突触的连接模式。使用GABA受体亚基特异性条件性敲除小鼠，我们将确定是否成熟的GABA能突触轴承α 1 GABAA受体亚基需要的α 3亚基的存在下，是短暂丰富的发展过程中。在目标2中，我们将采用成像，电生理检测，和突变小鼠干扰抑制性传递，以确定神经传递的作用，在建立适当的双极细胞轴突上的抑制性突触类型的组合。在目标3中，我们将区分在双极细胞的轴突与树突的不同细胞隔室中用于调节GABA能突触的通路。我们将使用分子和遗传学方法来改变细胞内氯通量 特别是在这些神经元中。我们的研究结果将大大促进对细胞 调节突触前抑制的发展和维持的机制，这些机制通过并行作用的回路来处理感觉信号。

DESCRIPTION (provided by applicant): The output of a neuron is shaped not only by excitation but also by the magnitude and timing of inhibition mediated by the neurotransmitters, gamma-aminobutyric acid (GABA) and glycine. Circuits become dysfunctional as found in many diseases of the nervous system when excitation is not controlled properly by inhibition. Our understanding of the cellular interactions that assemble and maintain appropriate inhibitory connections lags far behind our knowledge about excitatory circuits. In this project, we propose to significantly advance knowledge of the development and functional maintenance of inhibitory connections that control the release of excitatory neurotransmitters from axons. We will focus on inhibitory synapses on the axon terminals of retinal bipolar cells. These neurons are essential for relaying visual signals from photoreceptors to the retinal ganglion cells. Transmission from these cells is shaped by at least two different types of inhibitory synapses. In Aim 1, we will genetically label ionotropic GABAA and GABAC receptors that regulate inhibition onto the same axon, but with different kinetics. We will use correlative fluorescence imaging and serial block face scanning electron microscopy to map connectivity patterns of the different synapse types. Using GABA receptor subunit specific conditional knockout mice, we will determine whether mature GABAergic synapses bearing alpha1 GABAA receptor subunits require the presence of alpha3 subunits that are transiently abundant during development. In Aim 2, we will employ imaging, electrophysiological assays, and mutant mice with perturbed inhibitory transmission to ascertain the role of neurotransmission in establishing the appropriate combination of inhibitory synapse types on bipolar cell axons. In Aim 3, we will distinguish the pathways that are employed to regulate GABAergic synapses in distinct cell compartments, axon versus dendrite, of bipolar cells. We will use molecular and genetic approaches to alter intracellular chloride flux specifically in these neurons. Our results will significantly advance understanding of the cellular mechanisms that regulate the development and maintenance of presynaptic inhibition across circuits that act in parallel to process sensory signals.