DEVELOPMENTAL CONTROL OF SYNAPSE STRUCTURE WITH LTP

描述（申请人提供）：树突棘承载bbb90 %的兴奋性突触；在许多破坏中枢神经系统功能的发育障碍中，它们丢失或结构异常。总体目标是了解脊柱和突触结构在学习和记忆的正常发展中的作用。长期增强（LTP）是学习和记忆的突触模型，非常适合研究这一过程。脊柱被认为是重要的，因为它们隔离了蛋白质合成依赖或LTP （L-LTP）“晚期”阶段所需的核心结构和分子，这些结构和分子持续约30小时。一个清晰的认识需要纳米分辨率的三维重建从连续切片电子显微镜，在这个实验室开创的方法。树突棘的形成和突触结构的可塑性是否为海马体中L-LTP的发育调控提供了一般机制，海马体是大脑中学习和记忆的关键区域。目的1是验证在出生后12天突然出现的L-LTP与树突棘的首次出现和结构突触可塑性的能力有关的假设。实验将确定当L-LTP不是由一次TBS产生时，P12与P8和P10的树突、轴突、脊柱和突触结构和组成的区别。他们将测试在P12产生L-LTP是否会导致小棘的平衡消除和成熟海马中剩余突触的扩大，以及突触前和突触后的结构重塑是否在发育过程中与表达L-LTP的能力同步。目的2是验证假设树突棘是由TBS诱导的，然后在P10第二次TBS后维持L-LTP，而不是在P8，当多次TBS不产生L-LTP时。目的3是确定小鼠海马中L-LTP的发育开始及其超微结构相关因素，为未来使用遗传操作的工作奠定基础。这些研究成果有望对学习和记忆的突触基础有新的认识，这是设计有效治疗发育性大脑疾病的必要知识。

DESCRIPTION (provided by applicant): Dendritic spines host >90 percent of excitatory synapses; they are lost or have abnormal structure in many developmental disorders that disrupt central nervous system function. The overall goal is to understand the role of spine and synapse structure in the normal development of learning and memory. Long-term potentiation (LTP) is a synaptic model of learning and memory well-suited to investigate this process. Spines are thought to be important because they sequester core structures and molecules needed for the protein synthesis-dependent or "late" phase of LTP (L-LTP) lasting >3hr. A clear understanding requires the nanometer resolution of 3D reconstruction from serial section electron microscopy, an approach pioneered in this laboratory. Rigorous experiments are proposed to test whether formation of dendritic spines and structural synaptic plasticity provide general mechanisms for the developmental regulation of L-LTP in hippocampus, a brain region crucial for learning and memory. Aim 1 is to test the hypothesis that the abrupt onset of L-LTP at postnatal day (P)12 is associated with first occurrence of dendritic spines and capacity for structural synaptic plasticity. The experiments will determine what differentiates dendritic, axonal, spine, and synaptic structure and composition at P12, from P8 and P10 when L-LTP is not produced by one bout of TBS. They will test whether production of L-LTP at P12 results in a balanced elimination of small spines and enlargement of remaining synapses as occurs in mature hippocampus and whether pre- and postsynaptic structural remodeling are synchronized during development with the ability to express L-LTP. Aim 2 is to test the hypothesis that dendritic spines are induced by TBS and then serve to sustain L-LTP after a second bout of TBS at P10, but not at P8, when multiple TBS do not produce L-LTP. Aim 3 is to ascertain the developmental onset of L-LTP and its ultrastructural correlates in mouse hippocampus as a foundation for future work using genetic manipulations. The outcomes promise new insight into the synaptic basis of learning and memory, essential knowledge to design effective treatments for developmental brain disorders. PUBLIC HEALTH RELEVANCE: Synapses are structurally disrupted in individuals with developmental brain disorders. Normal development must be characterized to draw conclusions about functional consequences of such disruption. Here the nanometer resolution of electron microscopy, and long-term potentiation, a synaptic mechanism of learning and memory, are combined to investigate the normal development of synapse structure and function.