KCNQ2/3 channels in neonatal-onset epilepsy and encephalopathy

描述（由申请人提供）：KCNQ2或KCNQ3突变导致良性家族性新生儿癫痫发作（BFNS），这是一种显性遗传、高渗透的早发性癫痫综合征。BFNS在新生儿时期引起频繁的癫痫发作，但癫痫发作缓解后，受影响的个体发育正常。然而，现在有令人信服的证据表明，KCNQ2突变的一个子集存在于持续性和致残性中枢神经系统和神经肌肉疾病中。KCNQ2家系表现为疼痛性肌动障碍（无癫痫发作）、新生儿癫痫发作后的肌动障碍、新生儿期后的癫痫以及伴有显著智力残疾的癫痫。最重要的是，最近的一项欧洲-澳大利亚合作研究描述了10%（8/80）的严重、散发性、早发性癫痫性脑病（EEE）病例中KCNQ2突变的发生。正如这份更新申请中所披露的，我们的实验室已经确定了另外6名来自北美的EEE患者携带新的KCNQ2突变。虽然遗传背景和表观遗传学等因素可能会影响这些表型，但我们的分析表明，EEE患者中新生的KCNQ2突变可能是有效的显性阴性，抑制活性高达94%（16倍），而已知的BFNS突变通常会使活性降低20-50%（2倍或更少）。在这里，我们提出确定KCNQ2和含有kcnq3的通道到达海马区神经元轴突膜和体感觉和运动新皮层的发育时间过程，并在正常啮齿动物、KCNQ2突变小鼠和人类组织中进行了实验。在解剖研究的同时，我们还将通过体外分析、膜片钳记录和转基因动物模型，在亚细胞、细胞和行为水平上分析海马和新皮层轴突KCNQ通道的功能。最后，我们将分析和比较两种不同效价、最大功效和亚单位特异性的KCNQ打开剂在体外激活通道和体内终止癫痫发作的效果。

DESCRIPTION (provided by applicant): Mutations in KCNQ2 or KCNQ3 cause benign familial neonatal seizures (BFNS), a dominantly-inherited, highly penetrant early-onset epilepsy syndrome. BFNS causes frequent seizures during the neonatal period, but after seizures remit, affected individuals develop normally. However, compelling evidence now implicates a subset of KCNQ2 mutations in persistent and disabling CNS and neuromuscular diseases. KCNQ2 pedigrees exhibit painful myokymia (without seizures), myokymia after neonatal seizures, epilepsy after the neonatal period, and epilepsy with significant intellectual disability. Most importantly, a recent Euro-Australian collaborative study describes de novo KCNQ2 mutations in 10% of cases (8/80) of severe, sporadic, early- onset epileptic encephalopathy (EEE). As disclosed in this renewal application, our lab has ascertained 6 additional individuals from North America with EEE bearing novel KCNQ2 mutations. Although factors such as genetic background and epigenetics may influence these phenotypes, our analysis suggests mechanisms whereby the de novo KCNQ2 mutations in EEE patients may act as potent dominant-negatives, suppressing activity up to 94% (16-fold), whereas known BFNS mutations are known to generally reduce activity by 20-50% (2-fold or less). Here, we propose to define the developmental time course for the arrival of KCNQ2 and KCNQ3-containing channels at the axonal membrane of neurons in the hippocampal formation and the somatosensory and motor neocortex, assayed in normal rodents, KCNQ2 mutant mice, and human tissue. In parallel with anatomical study, we will also analyze the function of hippocampal and neocortical axonal KCNQ channels at the subcellular, cellular, and behavioral level through in vitro analysis, patch clamp recording, and transgenic animal models. Finally, we will analyze and compare the efficacy two KCNQ opener drugs which differ in potency, maximal efficacy and subunit specificity, to activate channels in vitro and terminate seizures in vivo.