Establishment of preventive strategies for nocturnal frontal lobe epilepsy-Elucidation of molecular mechanism to inhibit epileptic seizures

人类神经元烟碱乙酰胆碱受体(nAChR) α4、ss2或α2亚基（分别为CHRNA4、CHRNB2和CHRNA2）编码基因突变可引起夜间额叶癫痫（NFLE）。nfl相关癫痫发作仅在睡眠期间出现，并以三种不同的癫痫发作表型为特征；“阵发性觉醒”、“阵发性肌张力障碍”和“阵发性徘徊”。我们产生了含有错义突变S284L的转基因大鼠菌株，该突变已在NFLE的CHRNA4中被鉴定出来。转基因大鼠没有中枢神经系统畸形和行为异常等生物学异常。转基因（突变体Chrna4）的mRNA水平与野生型相似，在脑内未检测到畸变表达。然而，转基因大鼠在慢波睡眠（SWS）期间表现出与NFLE相似的癫痫发作表型，表现出三种特征性发作表型，从而符合人类NFLE的诊断标准。这些大鼠对常规抗癫痫药物的治疗反应也与S284L突变的NFLE患者相似。大鼠表现出两种主要的神经传递异常；1) SWS期间突触和突触外gaba能传递减弱，2)谷氨酸释放异常。目前可用的癫痫基因工程动物模型仅限于小鼠，因此，我们的转基因大鼠为癫痫研究领域提供了另一个维度。

Mutations of genes encoding α4, ss2 or α2 subunits (CHRNA4, CHRNB2 or CHRNA2, respectively), of neuronal nicotinic acetylcholine (ACh) receptor (nAChR) cause nocturnal frontal lobe epilepsy (NFLE) in human. NFLE-related seizures are seen exclusively during sleep and characterized by three distinct seizure phenotypes ; "paroxysmal arousals", "paroxysmal dystonia" and "episodic wandering". We generated transgenic rat strains that harbor a missense mutation S284L, which had been identified in CHRNA4 in NFLE. The transgenic rats were free of biological abnormalities, such as dysmorphology in the central nervous system, and behavioral abnormalities. The mRNA level of the transgene (mutant Chrna4) was similar to the wild-type and no distorted expression was detected in the brain. However, the transgenic rats showed epileptic seizure phenotypes during slow wave sleep (SWS) similar to those in NFLE exhibiting three characteristic seizure phenotypes and thus fulfilled the diagnostic criteria of human NFLE. The therapeutic response of these rats to conventional antiepileptic drugs also resembled that of NFLE patients with the S284L mutation. The rats exhibited two major abnormalities in neurotransmission ; 1) Attenuation of synaptic and extrasynaptic GABAergic transmission and 2) abnormal glutamate release during SWS. The currently available genetically engineered animal models of epilepsy are limited to mice, thus, our transgenic rats offer another dimension to the epilepsy research field.