基于脑内谷氨酸平衡探讨LGI1突变致癫痫的病理机制

LGI1突变导致人类常染色体显性侧颞叶癫痫（ADLTE），但病理机制尚不清楚。申请人团队近期在一个ADLTE家系中发现了新的LGI1_D51G突变，Lgi1D51G/D51G小鼠表现出生后早期癫痫大发作并致死的现象，然而该现象不能被目前已知的LGI1参与的神经功能损害所解释，提示LGI1尚有未知的神经功能。通过预实验，申请人发现了新的LGI1结合蛋白EAAT2（星形胶质细胞上谷氨酸转运体），LGI1缺失将导致EAAT2的表达下降和功能损伤。因此我们提出假说：LGI1是维持EAAT2正确定位和发挥功能的关键因素，LGI1缺失后EAAT2功能损伤，造成脑内谷氨酸失衡是导致癫痫大发作的关键机制。在本研究中，申请人将利用基因小鼠模型，结合分子生物学、生物化学和神经电生理研究方法探讨LGI1-EAAT2蛋白复合物在癫痫中的发病机制，从而揭示一种新的LGI1参与癫痫的病理机制。

LGI1 mutation causes human autosomal dominant lateral temporal lobe epilepsy (ADLTE). However, the pathological mechanism remains unclear. We identified a novel missense mutation, c.152A>G (p.Asp51Gly), on LGI1 from a ADLTE families. Lgi1D51G/D51G mice exhibit seizure outburst and death in the early postnatal period. This phenomenon cannot be explained by known neurological impairments involved in LGI1, suggesting that LGI1 may have unknown function. Through previous studies, we found a novel LGI1 binding protein - EAAT2 (glutamate transporter on astrocyte). The deletion of LGI1 led to EAAT2 expression decreased and function damaged. Based on these preliminary results, we propose that LGI1 is the key factor to maintain the correct localization and normal function of EAAT2. LGI1 mutations lead to the decrease of EAAT2 expression and its functional damage, followed by glutamate increased in the brain and grand mal seizures. Driven by this hypothesis, we will use the gene-manipulated mouse models, combined with molecular biological, biochemical and electrophysiological research methods to explore the mechanism of LGI1-EAAT2 protein complex involved in epilepsy. This study will reveal a novel pathological mechanism of LGI1 induced epilepsy.