依赖于GABA转运体-1的纹状体突触重塑新机制研究

Developmental synaptic remodeling is a highly-programmed process including both synapse formation during early postnatal stage and synapse elimination during adolescence. The aberrant regulation of synaptic remodeling and consequent synaptic dysfunction are the common cellular mechanisms underlying neurodevelopmental and psychiatric disorders. The applicant and the present project team are long engaged in the mechanistic studies on synapse development and plasticity with an emphasis on the involvement of transmembrane signaling in these processes. Recently, by taking advantage of a mouse model with excess γ-aminobutyric acid (GABA) by genetic deletion of GABA transporter-1 (GAT1), we raised a significant but not recognized role of the GAT1-dependent synaptic remodeling mechanism for striatal synapse maturation. Compared with the wild-type littermates, in the mutant animal, we found an increased excitability of striatal medium spiny neuron, a premature glutamatergic synapse onto these neurons at the structural and functional domains, a deficiency in the induction of long-term depression at corticostriatal synapses, and a significantly-reduced expression of endocannabinoids and their receptors in striatum. Based on these preliminary results, here we propose to deepen the mechanistic study on the GAT1-dependent striatal synaptic remodeling, aiming to reveal the cellular and molecular mechanisms underlying the homeostatic regulation of excitatory striatal synapse maturation by altering the inhibitory synapse inputs, by using multi-discipline approaches including electrophysiology, morphology, behavioral analysis, optogenetics, biochemistry and molecular cell biology, in addition to by virtue of genetic engineering mouse and AAV-mediated molecular genetics and in vivo pharmacological tools. The present project is expected to provide novel insights for the understanding of synaptic pathology occurred in the neurodevelopmental disorder, and to guide the translational medicine research.

神经发育阶段的突触重塑包括出生后早期突触的形成和青春期的突触消除等步骤，其调控异常是众多神经发育性疾病在细胞水平的共同病理基础。申请者及项目组长期开展神经跨膜信号调控与突触发育及可塑性的机制研究，最新发现γ-氨基丁酸（GABA）转运体-1基因缺陷导致青春期动物纹状体中型多棘神经元活性增高，谷氨酸能突触在结构与功能上“提前成熟”，同时，皮层-纹状体的兴奋性突触长时程抑制可塑性受损，伴随纹状体内源性大麻素合成酶及其受体表达降低。基于这些预实验结果，本项目将综合运用电生理学、形态学、行为学、光遗传学、生物化学与分子细胞生物学等多学科研究手段，借助基因工程修饰小鼠并结合病毒载体构建及在体干预等分子遗传学和药理学手段，研究依赖于GABA转运体-1的纹状体突触重塑新机制，致力于探讨神经环路特异的兴奋-抑制稳态平衡调节突触重塑的细胞和分子机制，为理解突触发育依赖的疾病机制提供新思路，指导转化医学研究。

神经发育阶段的突触重塑包括出生后早期突触的形成和青春期的突触消除等步骤，其调控异常是众多神经发育性疾病在细胞水平的共同病理基础。神经元的兴奋-抑制稳态平衡是一种普遍的生理现象，突触重塑机制发生异常会带来特定神经环路上兴奋和抑制的稳态失衡，从而引发神经发育性疾病相关的特征性病理行为。本项目聚焦神经发育阶段的突触重塑过程，选取纹状体兴奋性突触及其相关神经环路为研究对象，以广泛分布于中枢神经系统的GABA递质转运体——GABA转运体-1（GAT1）为研究基础，综合运用电生理学、形态学、行为学、光遗传学、生物化学与分子细胞生物学等多学科研究手段，借助基因工程修饰小鼠并结合病毒载体构建及在体干预等分子遗传学和药理学手段，深入系统地研究了依赖于GAT1的纹状体突触重塑新机制，揭示了神经环路特异的兴奋-抑制稳态平衡调节突触重塑的细胞和分子机制，为理解突触发育依赖的疾病机制提供了新思路。在此基础上，发展纹状体突触重塑新机制指导下的神经发育性疾病干预新策略，指导转化医学研究。本项目在《National Science Review》、《Molecular Psychiatry》、《Science Advances》、《Science Signaling》等国际学术期刊发表论文8篇。协助培养博士研究生毕业4人，并以联合培养的方式为国内合作单位培养研究生毕业5人；培养项目成员获各类资助项目、奖励或人才计划13项；项目组成员参加国内外学术会议21人次，圆满完成了预期目标。