Special electromyographic features in a child with paramyotonia congenita: A case report and review of literature

BACKGROUND Paramyotonia congenita(PMC)stands as a rare sodium channelopaty of skeletal muscle,initially identified by Eulenburg.The identification of PMC often relies on electromyography(EMG),a diagnostic technique.The child’s needle EMG unveiled trains of myotonic discharges with notably giant amplitudes,alongside irregular wave trains of myotonic discharges.This distinctive observation had not surfaced in earlier studies.CASE SUMMARY We report the case of a 3-year-old female child with PMC,who exhibited la-ryngeal stridor,muffled speech,myotonia from birth.Cold,exposure to cool water,crying,and physical activity exacerbated the myotonia,which was relieved in warmth,yet never normalized.Percussion myotonia was observable in bilateral biceps.Myotonia symptoms remained unchanged after potassium-rich food consumption like bananas.Hyperkalemic periodic paralysis was excluded.Cranial magnetic resonance imaging yielded normal results.Blood potassium remained within normal range,while creatine kinase showed slight elevation.Exome-wide genetic testing pinpointed a heterozygous mutation on chromosome SCN4A:c.3917G>A(p.G1306E).After a six-month mexiletine regimen,symptoms alleviated.CONCLUSION In this case revealed the two types of myotonic discharges,and had not been documented in other studies.We underscore two distinctive features:Giant-amplitude potentials and irregular waves.

骨骼肌离子通道病的研究近况

离子通道病是近年新兴的一门交叉型前沿学科。所谓离子通道病（ion channelopathy,ICP or ion channel disease,ICD）是指当编码离子通道亚单位的基因发生突变/表达异常或体内出现针对通道的病理性内源物质时,使通道的功能出现不同程度的削减或增强,从而导致机体整体生理功能的紊乱,导致某些先天性和后天获得性疾病。

复旦大学生命科学学院桑庆、王磊研究团队合作研究首次发现并命名人类新遗传疾病“卵子死亡”

复旦大学生命科学学院、遗传工程国家重点实验室桑庆副研究员和王磊教授团队与上海交通大学医学院附属第九人民医院生殖中心匡延平教授团队合作研究首次发现了一种新的人类遗传病,将其命名为“卵子死亡”。该研究明确了疾病的致病基因为细胞连接蛋白家族成员PANX1存在突变,并通过细胞水平、爪蟾卵子、鼠模型等多个角度深入揭示了致病机制,即突变通过影响蛋白糖基化、激活通道、加速ATP释放,致使表型出现。从而证明“卵子死亡”是一种全新的孟德尔遗传病及糖基化疾病,也是PANX家族成员异常的首个离子通道疾病。2019年3月28日,这一研究成果以“A pannexin 1 channelopathy causes human oocyte death”为题在线发表于Science杂志子刊Science Translational Medicine。

Syncope and Early Repolarization:A Benign or Dangerous ECG Finding?

Early repolarization is a well-described,common electrocardiographic variant.It was initially felt to be benign,but in the last twenty years a suggested a link between specific types of early repolarization and sudden cardiac death has emerged.This association was has been termed the J wave syndrome and includes both the high risk early repolarization and Brugada ECG patterns.The odds of early repolarization change being associated with poor outcomes are still exceedingly small.Nevertheless,the association of a fairly ubiquitous ECG finding with fatal or near fatal clinical outcomes has raised concern.How can we identify the truly high-risk patients?If a patient has a signifi cant clinical event with a concerning ECG repolarization pattern,what should be done next?The authors of this review present current information regarding the Early Repolarization and Brugada Syndromes and how to proceed with diagnosis,management,and risk stratifi cation when early repolarization change is observed on ECG.

Patient-specific induced pluripotent stem cells as“disease-in-adish”models for inherited cardiomyopathies and channelopathies–15 years of research

Among inherited cardiac conditions,a special place is kept by cardiomyopathies(CMPs)and channelopathies(CNPs),which pose a substantial healthcare burden due to the complexity of the therapeutic management and cause early mortality.Like other inherited cardiac conditions,genetic CMPs and CNPs exhibit incomplete penetrance and variable expressivity even within carriers of the same pathogenic deoxyribonucleic acid variant,challenging our understanding of the underlying pathogenic mechanisms.Until recently,the lack of accurate physiological preclinical models hindered the investigation of fundamental cellular and molecular mechanisms.The advent of induced pluripotent stem cell(iPSC)technology,along with advances in gene editing,offered unprecedented opportunities to explore hereditary CMPs and CNPs.Hallmark features of iPSCs include the ability to differentiate into unlimited numbers of cells from any of the three germ layers,genetic identity with the subject from whom they were derived,and ease of gene editing,all of which were used to generate“disease-in-a-dish”models of monogenic cardiac conditions.Functionally,iPSC-derived cardiomyocytes that faithfully recapitulate the patient-specific phenotype,allowed the study of disease mechanisms in an individual-/allele-specific manner,as well as the customization of therapeutic regimen.This review provides a synopsis of the most important iPSC-based models of CMPs and CNPs and the potential use for modeling disease mechanisms,personalized therapy and deoxyribonucleic acid variant functional annotation.

Web Control System for Transcorneal Electric Stimulation Devices

The electrical stimulation systems dedicated to generating unconventional waveforms have been shown to have a positive effect in the treatment of channelopathies, for example, in open-angle glaucoma. However, these signals can be distorted due to different external circumstances, which could lead to counterproductive effects in treatments such as increased intraocular pressure IOP or other effects that are unknown due to poor electrical signaling. In the present work, a web control system capable of communicating with transcorneal electrical stimulation equipment is proposed for the remote control of treatments applied to patients suffering from various ocular channelopathies. As the first phase of this system, it will only focus on treating patients with open-angle glaucoma since this disease is characterized by an increase in IOP and can be immediately measured by an ophthalmologist.

Voltage-gated Sodium Channels and Blockers:An Overview and Where Will They Go?

Voltage-gated sodium(Nav)channels are critical players in the generation and propagation of action potentials by triggering membrane depolarization.Mutations in Nav channels are associated with a variety of channelopathies,which makes them relevant targets for pharmaceutical intervention.Sofar,the cryoelectron microscopic structure of the human Nav 1.2,Nav 1.4,and Nav 1.7 has been reported,which sheds light on the molecular basis of functional mechanism of Nav channels and provides a path toward structure-based drug discovery.In this review,we focus on the recent advances in the structure,molecular mechanism and modulation of Nav channels,and state updated sodium channel blockers for the treatment of pathophysiology disorders and briefly discuss where the blockers may be developed in the future.

Both gain-and loss-of-function variants of KCNA1 are associated with paroxysmal kinesigenic dyskinesia

KCNA1 is the coding gene for Kv1.1 voltage-gated potassium-channelαsubunit.Three variants of KCNA1 have been reported to manifest as paroxysmal kinesigenic dyskinesia(PKD),but the correlation between them remains unclear due to the phenotypic complexity of KCNA1 variants as well as the rarity of PKD cases.Using the whole exome sequencing followed by Sanger sequencing,we screen for potential pathogenic KCNA1 variants in patients clinically diagnosed with paroxysmal movement disorders and identify three previously unreported missense variants of KCNA1 in three unrelated Chinese families.The proband of one family(c.496G>A,p.A166T)manifests as episodic ataxia type 1,and the other two(c.877G>A,p.V293I and c.1112C>A,p.T371A)manifest as PKD.The pathogenicity of these variants is confirmed by functional studies,suggesting that p.A166T and p.T371A cause a loss-of-function of the channel,while p.V293I leads to a gain-of-function with the property of voltage-dependent gating and activation kinetic affected.By reviewing the locations of PKD-manifested KCNA1 variants in Kv1.1 protein,we find that these variants tend to cluster around the pore domain,which is similar to epilepsy.Thus,our study strengthens the correlation between KCNA1 variants and PKD and provides more information on genotype–phenotype correlations of KCNA1 channelopathy.

Structure-based assessment of disease- related mutations in human voltage-gated sodium channels

Voltage-gated sodium （Nav） channels are essential for the rapid upstroke of action potentials and the propa- gation of electrical signals in nerves and muscles. Defects of Nav channels are associated with a variety of channelopathies. More than 1000 disease-related muta- tions have been identified in Nay channels, with Nay1.1 and Nay1.5 each harboring more than 400 mutations. Nay channels represent major targets for a wide array of neurotoxins and drugs. Atomic structures of Nav chan- nels are required to understand their function and dis- ease mechanisms. The recently determined atomic structure of the rabbit voltage-gated calcium （Car） channel Carl.1 provides a template for homology-based structural modeling of the evolutionarily related Nay channels. In this Resource article, we summarized all the reported disease-related mutations in human Nav channels, generated a homologous model of human Nay1.7, and structurally mapped disease-associated mutations. Before the determination of structures of human Nay channels, the analysis presented here serves as the base framework for mechanistic investi- gation of Nav channelopathies and for potential struc- ture-based drug discovery.

Exercise test on the patients with normokalaemic periodic paralysis from a Chinese family with a mutation in the SCN4A gene

Background Normokalaemic periodic paralysis （normoKPP） is characterized by transient and recurrent myoasthenia, and some patients also show muscle stiffness induced by cold exposure （paramyotonia congenita, PMC）. It is caused by a mutation in the muscle voltage gated sodium channel alpha subunit （SCN4A） gene. Due to the diversity of the clinical manifestations of patients, it is difficult for clinicians to differentiate some of patients with atypical normoKPP from those who suffer from other periodic paralysis and nondystrophic myotonia. So far, for normoKPP there are almost no ways to assist definite diagnosis besides genetic screening. This research was designed to evaluate an exercise test （ET） in confirming the diagnosis of normoKPP and in assessing the therapeutic effectiveness of some drugs on this disease. Methods ET, described by McMains, was performed on six subjects from a Chinese family, including four patients with overlapping disease of normoKPP and PMC caused by a mutation of SCN4A Met1592Val that is identified by genetic analysis and two normal control members. The change of compound muscle action potential （CMAP） was recorded. Besides the family, two patients were also tested during treatments with acetazolamide. Results All patients showed a slight increase in CMAP immediately after exercise, followed by an abnormal gradual decline, which reached its nadir 25-30 minutes after exercise. CMAP amplitude dropped by more than 40% in patients but less than 23% in controls. In the patients who received treatment with acetazolamide, the change of CMAP amplitude was less than 28% and, at any fixed times, less than pretreatment values. Conclusions The ET may be used as a predictive, easy and reliable method of diagnosing normoKPP under conditions without genetic screening help, and is an objective way to evaluate the therapeutic effectiveness. According to different response patterns, the ET may also be helpful in reducing the scope of genetic screening.

Highlights for the 6th International Ion Channel Conference:ion channel structure,function,disease and therapeutics

To foster communication and interactions amongst international scholars and scientists in the field of ion channel research, the 6 th International Ion Channel Conference(IICC-2017) was held between June 23–27, 2017 in the eastern coastal city of Qingdao, China. The meeting consisted of 450 attendees and 130 speakers and poster presenters. The program consisted of research progress, new findings and ongoing studies that were focused on(1) Ion channel structure and function;(2) Ion channel physiology and human diseases;(3) Ion channels as targets for drug discovery;(4) Technological advances in ion channel research. An insightful overview was presented on the structure and function of the mechanotransduction channel Drosophila NOMPC(No mechanoreceptor potential C), a member of the transient receptor potential(TRP) channel family. Recent studies on Transmembrane protein 16 or Anoctamin-1(TMEM16A, a member of the calcium-activated chloride channel [CaCC] family) were summarized as well. In addition, topics for ion channel regulation, homeostatic feedback and brain disorders were thoroughly discussed. The presentations at the IICC-2017 offer new insights into our understanding of ion channel structures and functions, and ion channels as targets for drug discovery.

Ion channel-related hereditary hearing loss:a narrative review

Sensorineural hearing loss is the most common sensory deficit in humans,with an estimated prevalence of 1 in 500 newborns.Approximately half of childhood hearing loss is attributed to genetic factors and can be classified as syndromic or non-syndromic based on the inheritance pattern.The ion channel genesKCNQ1,KCNE1,KCNQ4,P2RX2,TMC1,KCNJ10,andCACNA1D have frequently been associated with genetic hearing loss.Because of the important roles these genes play in cochlear hair cell function and the auditory pathways,mutations in these genes that result in impaired ion channel function can lead to hereditary hearing loss.The main purpose of this review was to examine the latest research progress on the functional roles,inheritance pattern,gene expression,protein structure,clinical phenotypes,mouse models,and possible treatments of the most commonly studied ion channels associated with inherited deafness.A comprehensive summary could help highlight ion channels that should be investigated as potential drug targets for the treatment of inherited deafness.