Department of Neurology, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China.
Department of Physiology, Institute of Neuroscience, Key Laboratory of Medical Neurobiology of Ministry of Health of China, Zhejiang Province Key Laboratory of Tissue Engineering and Regenerative Medicine, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China.
J Physiol. 2017 Nov 15;595(22):6837-6850. doi: 10.1113/JP274877. Epub 2017 Oct 15.
Paramyotonia congenita is a hereditary channelopathy caused by missense mutations in the SCN4A gene, which encodes the α subunit of the human skeletal muscle voltage-gated sodium channel NaV1.4. Affected individuals suffered from myotonia and paralysis of muscles, which were aggravated by exposure to cold. We report a three-generation Chinese family with patients presenting paramyotonia congenita and identify a novel N1366S mutation of NaV1.4. Whole-cell electrophysiological recordings of the N1366S channel reveal a gain-of-function change of gating in response to cold. Modelling and molecular dynamic simulation data suggest that an arginine-to-serine substitution at position 1366 increases the distance from N1366 to R1454 and disrupts the hydrogen bond formed between them at low temperature. We demonstrate that N1366S is a disease-causing mutation and that the temperature-sensitive alteration of N1366S channel activity may be responsible for the pronounced paramyotonia congenita symptoms of these patients.
Paramyotonia congenita is an autosomal dominant skeletal muscle channelopathy caused by missense mutations in SCN4A, the gene encoding the α subunit of the human skeletal muscle voltage-gated sodium channel NaV1.4. We report a three-generation family in which six members present clinical symptoms of paramyotonia congenita characterized by a marked worsening of myotonia by cold and by the presence of clear episodes of paralysis. We identified a novel mutation in SCN4A (Asn1366Ser, N1366S) in all patients in the family but not in healthy relatives or in 500 normal control subjects. Functional analysis of the channel protein expressed in HEK293 cells by whole-cell patch clamp recording revealed that the N1366S mutation led to significant alterations in the gating process of the NaV1.4 channel. The N1366S mutant displayed a cold-induced hyperpolarizing shift in the voltage dependence of activation and a depolarizing shift in fast inactivation, as well as a reduced rate of fast inactivation and accelerated recovery from fast inactivation. In addition, homology modelling and molecular dynamic simulation of N1366S and wild-type NaV1.4 channels indicated that the arginine-to-serine substitution disrupted the hydrogen bond formed between N1366 and R1454. Together, our results suggest that N1366S is a gain-of-function mutation of NaV1.4 at low temperature and the mutation may be responsible for the clinical symptoms of paramyotonia congenita in the affected family and constitute a basis for studies into its pathogenesis.
先天性肌强直是一种遗传性通道病，由 SCN4A 基因的错义突变引起，该基因编码人类骨骼肌电压门控钠通道 NaV1.4 的 α 亚基。受影响的个体患有肌强直和肌肉瘫痪，在接触寒冷时会加重。我们报告了一个三代中国家庭，患者表现出先天性肌强直，并鉴定出 NaV1.4 的一种新的 N1366S 突变。全细胞电生理记录显示，冷刺激下门控的功能获得性改变。建模和分子动力学模拟数据表明，第 1366 位的精氨酸到丝氨酸取代增加了 N1366 与 R1454 之间的距离，并在低温下破坏了它们之间形成的氢键。我们证明 N1366S 是一种致病突变，N1366S 通道活性的温度敏感性改变可能是这些患者明显先天性肌强直症状的原因。
先天性肌强直是一种常染色体显性遗传性骨骼肌通道病，由 SCN4A 基因的错义突变引起，该基因编码人类骨骼肌电压门控钠通道 NaV1.4 的 α 亚基。我们报告了一个三代家系，其中 6 名成员表现出先天性肌强直的临床症状，其特征是寒冷时肌强直明显加重，并有明显的瘫痪发作。我们在家族中的所有患者中发现了 SCN4A 的一种新突变（Asn1366Ser，N1366S），但在健康亲属或 500 名正常对照中未发现该突变。通过全细胞膜片钳记录对在 HEK293 细胞中表达的通道蛋白进行功能分析表明，N1366S 突变导致 NaV1.4 通道门控过程的显著改变。N1366S 突变体显示出激活的电压依赖性的冷诱导超极化偏移和快速失活的去极化偏移，以及快速失活的速率降低和快速失活的恢复加速。此外，N1366S 和野生型 NaV1.4 通道的同源建模和分子动力学模拟表明，精氨酸到丝氨酸的取代破坏了 N1366 和 R1454 之间形成的氢键。总之，我们的结果表明，N1366S 是 NaV1.4 的低温功能获得性突变，该突变可能是导致受影响家族中先天性肌强直临床症状的原因，并为其发病机制的研究提供了依据。
