Genotype-phenotype correlations in neonatal epilepsies caused by mutations in the voltage sensor of Kv7.2 potassium channel subunits
Genotype-phenotype correlations in neonatal epilepsies caused by mutations in the voltage sensor of Kv7.2 potassium channel subunits
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DOI：
10.1073/pnas.1216867110
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发表时间：
2013-03-12
影响因子：
11.1
通讯作者：
Taglialatela, Maurizio
中科院分区：
文献类型：
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作者：
Miceli, Francesco;Soldovieri, Maria Virginia;Taglialatela, Maurizio
编码电压依赖性K+通道亚基的K（v）7.2基因突变导致新生儿癫痫，具有广泛的表型异质性。在患有良性家族性新生儿癫痫发作（R213 W突变）或患有新生儿癫痫性脑病伴严重药物耐药性癫痫发作和神经认知延迟、EEG抑制爆发模式和明显神经放射学特征（R213 Q突变）的儿童中发现了影响K（v）7.2的54结构域中相同带正电荷残基的两种突变。为了研究这种截然不同的表型的分子基础，我们研究了突变通道的功能特性，通过使用电生理技术，计算建模，同源建模。功能研究表明，在同聚体或异聚体结构与K（v）7.2和/或K（v）7.3亚基，这两个突变显着不稳定的开放状态，导致通道电压敏感性急剧下降。这些功能变化是（i）更明显的通道，并结合R213 Q-比R213 W-携带K（v）7.2亚基;（ii）成比例的突变亚基的数量纳入;和（iii）完全恢复神经元K（v）7激活剂瑞替加滨。同源性建模证实了R213残基在稳定激活的电压传感器配置中的关键作用。在CA 1海马锥体细胞中的建模实验显示，这两种突变都增加了细胞放电频率，与R213 W突变相比，R213 Q突变引起了更显著的功能变化。这些结果表明，临床疾病的严重程度可能与突变诱导的功能性K+通道受损的程度有关，并为K（v）7开放剂作为靶向抗惊厥治疗的潜在用途奠定了临床前基础，以改善患有K（v）7.2脑病的新生儿的发育结局。
Mutations in the K(v)7.2 gene encoding for voltage-dependent K+ channel subunits cause neonatal epilepsies with wide phenotypic heterogeneity. Two mutations affecting the same positively charged residue in the 54 domain of K(v)7.2 have been found in children affected with benign familial neonatal seizures (R213W mutation) or with neonatal epileptic encephalopathy with severe pharmacoresistant seizures and neurocognitive delay, suppression-burst pattern at EEG, and distinct neuroradiological features (R213Q mutation). To examine the molecular basis for this strikingly different phenotype, we studied the functional characteristics of mutant channels by using electrophysiological techniques, computational modeling, and homology modeling. Functional studies revealed that, in homomeric or heteromeric configuration with K(v)7.2 and/or K(v)7.3 subunits, both mutations markedly destabilized the open state, causing a dramatic decrease in channel voltage sensitivity. These functional changes were (i) more pronounced for channels incorporating R213Q- than R213W-carrying K(v)7.2 subunits; (ii) proportional to the number of mutant subunits incorporated; and (iii) fully restored by the neuronal K(v)7 activator retigabine. Homology modeling confirmed a critical role for the R213 residue in stabilizing the activated voltage sensor configuration. Modeling experiments in CA1 hippocampal pyramidal cells revealed that both mutations increased cell firing frequency, with the R213Q mutation prompting more dramatic functional changes compared with the R213W mutation. These results suggest that the clinical disease severity may be related to the extent of the mutation-induced functional K+ channel impairment, and set the preclinical basis for the potential use of K(v)7 openers as a targeted anticonvulsant therapy to improve developmental outcome in neonates with K(v)7.2 encephalopathy.