The role of neuroligin-3 and neuroligin-4 in synaptic transmission, long-term synaptic plasticity and excitation/inhibition balance in dentate granule cells

海马体的齿状回对学习和记忆很重要。齿状神经网络中有效的信息处理需要在激发和抑制之间取得良好的平衡。这种平衡是由兴奋性和抑制性突触的分子参与者控制的。因此，在本项目提案中，我们将重点研究神经球蛋白（NLs）。神经胶质素形成一组突触蛋白，在平衡兴奋和抑制方面发挥关键作用，正如我们之前对NL1和NL2的研究所表明的那样。NL3和NL4是临床上最重要的神经素，因为NL3和NL4的基因突变与自闭症谱系障碍有关。兴奋和抑制之间的不平衡被认为是自闭症发病机制的核心机制。然而，NL3和NL4对兴奋-抑制平衡的调节作用尚不清楚。因此，在本项目提案中，我们关注NL3和nl4依赖的兴奋性和抑制性突触传递微调机制。我们的主要问题是：NL3和NL4如何影响齿状颗粒细胞及其主要兴奋性输入突触的功能特性？颗粒细胞中NL3或NL4的缺失是否会导致其兴奋性或突触输入特性和突触可塑性受损？NL3和NL4如何影响齿状回回路的体内网络活动？NL3或NL4缺失对网络抑制的影响是什么？NL3或NL4表达改变对齿状颗粒细胞选择性兴奋/抑制平衡的影响是什么？NL3或NL4是否参与维持齿状颗粒细胞的正常输出？本项目采用一种新颖的实验方法来揭示NL3和NL4在活体动物齿状回中的作用。具体而言，该项目建议使用电生理记录与神经组织学方法相结合，在细胞和网络水平上揭示齿状回颗粒细胞NL3和NL4丢失的功能影响。我们将使用有条件的、细胞类型特异性敲除NL3来研究齿状颗粒细胞中NL3选择性缺失的影响。我们的目的是研究NL3和NL4在齿状回中的作用(1)体内，通过在活体动物完整齿状回回路中使用细胞外场电位记录；(2)离体和体外，通过细胞内膜片钳记录和免疫组织学分析。结合遗传学、功能性和形态学的方法，我们可以检验关于NL3和NL4对齿状回内抑制和兴奋平衡的影响的假设。

The dentate gyrus of the hippocampus is important for learning and memory. Efficient processing of information in the dentate network requires a fine balance of excitation and inhibition. This balance is controlled by molecular players at excitatory and inhibitory synapses. Therefore, in this project proposal, we focus on neuroligins (NLs). Neuroligins form a group of synaptic proteins, which play a critical role in balancing excitation and inhibition, as has been shown by our previous work on NL1 and NL2. NL3 and NL4 are clinically the most important neuroligins since gene mutations in NL3 and NL4 have been associated with autism spectrum disorders. Dysbalance between excitation and inhibition is thought to be the central mechanism underlying the pathogenesis of autism. However the regulation of the excitation-inhibition balance by NL3 and NL4 is poorly understood. Therefore, in this project proposal we focus on NL3- and NL4-dependent mechanisms for fine-tuning of excitatory and inhibitory synaptic transmission. Our main questions are: How do NL3 and NL4 influence the functional properties of dentate granule cells and their major excitatory input synapses? Does the loss of NL3 or NL4 in granule cells lead to impairments of their excitability or synaptic input properties and synaptic plasticity? How do NL3 and NL4 influence the in vivo network activity in the dentate gyrus circuitry? What are the effects of NL3 or NL4 deletion on network inhibition? What are the effects of altered NL3 or NL4 expression on excitation/inhibition balance selectively in dentate granule cells? Do NL3 or NL4 participate in maintaining normal output of dentate granule cells?This project pursues a novel experimental approach to uncover the role of NL3 and NL4 in the dentate gyrus of live animals. Specifically, the project proposes to use electrophysiological recordings in combination with neurohistological methods to unravel, at a cellular and network level, the functional impact of NL3 and NL4 loss in granule cells of the dentate gyrus. We will use conditional, cell-type specific knockout of NL3 to investigate the effects of selective deletion of NL3 in dentate granule cells. We aim to study the role of NL3 and NL4 in the dentate gyrus (1) in vivo, by using extracellular field potential recordings in the intact dentate gyrus circuitry of live animals, (2) ex vivo and in vitro, by using intracellular patch-clamp recordings and performing immunohistological analyses. The combination of genetic, functional and morphological methods will allow us to test the hypotheses concerning NL3 and NL4 effects on the balance of inhibition and excitation within the dentate gyrus.