Project 7: Dynamics of Synapse Formation and Elimination in vivo

该项目的核心假设是，大脑的长期可塑性在很大程度上是由神经元回路的形态重组介导的，特别是通过选择性形成和消除突触。虽然这是一个广泛持有的信念，但突触的周转在体内的特征最少，并且对控制突触重塑的发育，环境和活动依赖性因素知之甚少，特别是在发育过程中。 完整的动物我们将产生PSD-95-GFP转基因小鼠和大鼠与荧光标记的突触的时间推移成像的突触形成和消除（营业额）在中枢神经元。我们将测量体内突触转换的模式和调节，目的是将这些变化与可塑性和行为联系起来。来自这些转基因动物的神经元培养物将用于研究这些转基因动物的分子和生理机制， 控制突触动力学我们的具体目标是：1）创建在组成型启动子下表达PSD-95-GFP的转基因小鼠，以标记脑中的兴奋性突触; 2）创建在活性诱导型启动子下表达不稳定PSD-95-GFP的转基因小鼠，以选择性标记最近活跃的神经元中新形成的突触; 3）使用新开发的慢病毒技术，创建在组成型和活性诱导型启动子下表达PSD-95-GFP的转基因大鼠; 4）使用转基因PSD-95-GFP动物表征出生后发育期间视皮层中突触更新的动力学及其通过视觉输入的调节; 5）使用来自PSD-95-GFP动物的培养神经元表征体外突触更新的时空模式和潜在机制。与Tonegawa，Bear和Liu合作，该提案使用多学科方法来探索神经元内的突触相互作用，以及皮层可塑性与学习和记忆的形态学相关性。 该项目有助于实现中心的多个目标，并依赖于综合科学专门知识和 中心的设施。

The central hypothesis of this project is that long-term plasticity of the brain is mediated in large part by morphological reorganization of neuronal circuits, and specifically by the selective formation and elimination of synapses. Although this is a widely held belief, the turnover of synapses has been minimally characterized in vivo, and little is known about the developmental, environmental and activity-dependent factors that control synapse remodeling, especially in the intact animal. We will produce PSD-95-GFP transgenic mice and rats with fluorescently-labeled synapses for time-lapse imaging of synapse formation and elimination (turnover) in central neurons. We will measure the pattern and regulation of synapse turnover in vivo, with the goal of correlating these changes to plasticity and behavior. Neuron cultures from these transgenic animals will be used to investigate the molecular and physiological mechanisms that control synapse dynamics. Our specific aims are: 1) Create transgenic mice expressing PSD-95-GFP under a constitutive promoter to label excitatory synapses in brain; 2) Create transgenic mice expressing unstable PSD-95-GFP under an activity-inducible promoter to selectively label newly formed synapses in recently active neurons; 3) Create transgenic rats expressing PSD-95-GFP under constitutive and activity-inducible promoters, using newly developed lentiviral technology; 4) Characterize the dynamics of synapse turnover in visual cortex during postnatal development and its regulation by visual input, using the transgenic PSD-95-GFP animals; 5) Characterize the spatiotemporal patterns and underlying mechanisms of synapse turnover in vitro, using cultured neurons derived from the PSD-95-GFP animals. In collaboration with Tonegawa, Bear, and Liu, this proposal uses a multidisciplinary approach to explore synaptic interactions within neurons, and the morphological correlates of cortical plasticity and learning and memory. The project contributes to multiple objectives of the Center and depends on the combined scientific expertise and facilities of the Center.