Mutations In SCN5A Gene Research Articles

Large-scale structural alteration of brain in epileptic children with SCN1A mutation.

ObjectiveMutations in SCN1A gene encoding the alpha 1 subunit of the voltage gated sodium channel are associated with several epilepsy syndromes including genetic epilepsy with febrile seizures plus (GEFS +) and severe myoclonic epilepsy of infancy (SMEI). However, in most patients with SCN1A mutation, brain imaging has reported normal or non-specific findings including cerebral or cerebellar atrophy. The aim of this study was to investigate differences in brain morphometry in epileptic children with SCN1A mutation compared to healthy control subjects.MethodsWe obtained cortical morphology (thickness, and surface area) and brain volume (global, subcortical, and regional) measurements using FreeSurfer (version 5.3.0, https://surfer.nmr.mgh.harvard.edu) and compared measurements of children with epilepsy and SCN1A gene mutation (n = 21) with those of age and gender matched healthy controls (n = 42).ResultsCompared to the healthy control group, children with epilepsy and SCN1A gene mutation exhibited smaller total brain, total gray matter and white matter, cerebellar white matter, and subcortical volumes, as well as mean surface area and mean cortical thickness. A regional analysis revealed significantly reduced gray matter volume in the patient group in the bilateral inferior parietal, left lateral orbitofrontal, left precentral, right postcentral, right isthmus cingulate, right middle temporal area with smaller surface area and white matter volume in some of these areas. However, the regional cortical thickness was not significantly different in two groups.SignificanceThis study showed large-scale developmental brain changes in patients with epilepsy and SCN1A gene mutation, which may be associated with the core symptoms of the patients. Further longitudinal MRI studies with larger cohorts are required to confirm the effect of SCN1A gene mutation on structural brain development.

SCN1A Gene Mutation and Adaptive Functioning in 18 Vietnamese Children with Dravet Syndrome.

Background and PurposeDravet syndrome is a rare and severe type of epilepsy in infants. The heterogeneity in the overall intellectual disability that these patients suffer from has been attributed to differences in genetic background and epilepsy severity.MethodsEighteen Vietnamese children diagnosed with Dravet syndrome were included in this study. SCN1A variants were screened by direct sequencing and multiplex ligation-dependent probe amplification. Adaptive functioning was assessed in all patients using the Vietnamese version of the Vineland Adaptive Behavior Scales, and the results were analyzed relative to the SCN1A variants and epilepsy severity.ResultsWe identified 13 pathogenic or likely pathogenic variants, including 6 that have not been reported previously. We found no correlations between the presence or type of SCN1A variants and the level of adaptive functioning impairment or severity of epilepsy. Only two of nine patients aged at least 5 years had an adaptive functioning score higher than 50. Both of these patients had a low frequency of convulsive seizures and no history of status epilepticus or prolonged seizures. The remaining seven had very low adaptive functioning scores (39 or less) despite the variability in the severity of their epilepsy confirming the involvement of factors other than the severity of epilepsy in determining the developmental outcome.ConclusionsOur study expands the spectrum of known SCN1A variants and confirms the current understanding of the role of the genetic background and epilepsy severity in determining the developmental outcome of Dravet syndrome patients.

Effects of S906T polymorphism on the severity of a novel borderline mutation I692M in Nav 1.4 cause periodic paralysis.

Hyperkalemic periodic paralysis (HyperPP) is a dominantly inherited muscle disease caused by mutations in SCN4A gene encoding skeletal muscle voltage gated Nav 1.4 channels. We identified a novel Nav 1.4 mutation I692M in 14 families out of the 104 genetically identified HyperPP families in the Neuromuscular Centre Ulm and is therefore as frequent as I693T (13 families out of 14 HyperPP families) in Germany. Surprisingly, in 13 families, a known polymorphism S906T was also present. It was on the affected allele in at least 10 families compatible with a possible founder effect in central Europe. All affected members suffered from episodic weakness; myotonia was also common. Compared with I692M patients, I692M-S906T patients had longer weakness episodes, more affected muscles, CK elevation and presence of permanent weakness. Electrophysiological investigation showed that both mutants had incomplete slow inactivation and a hyperpolarizing shift of activation which contribute to membrane depolarization and weakness. Additionally, I692M-S906T significantly enhanced close-state fast inactivation compared with I692M alone, suggesting a higher proportion of inactivated I692M-S906T channels upon membrane depolarization which may facilitate the initiation of weakness episodes and therefore clinical manifestation. Our results suggest that polymorphism S906T has effects on the clinical phenotypic and electrophysiological severity of a novel borderline Nav 1.4 mutation I692M, making the borderline mutation fully penetrant.

Variability in local action potential durations, dispersion of repolarization and wavelength restitution in aged wild-type and Scn5a+/- mouse hearts modeling human Brugada syndrome.

Brugada syndrome is a primary arrhythmia syndrome characterized by loss-of-function mutations in the SCN5A gene, which encodes for the cardiac Na+ channel. In affected individuals, the risk of developing malignant ventricular arrhythmias and sudden cardiac death are increased.[1] Two leading theories, the depolarization and repolarization hypotheses, have been put forward to explain the underlying electrophysiological mechanisms[2] with the use of mouse models providing much insight into this controversial area. The monophasic action potential (MAP) recording technique has been extensively used to examine electrophysiology at the whole heart level.[3] This letter attempts to provide a brief overview to illustrate the importance of understanding the limitations of experimental methods and the need to appraise experimental data.

Phenotype and gene mutation screening in familial Dravet syndrome

Objective To summarize the phenotype and gene mutation in familial Dravet syndrome (DS) and provide guidance for genetic counseling. Methods The clinical data and peripheral blood DNA samples of familial DS patients and their parents were collected from February 2005 to March 2016 in Department of Pediatrics, Peking University First Hospital.SCN1A mutations were screened by adopting Sanger sequencing and multiple ligation-dependent probe amplification (MLPA). Next generation sequencing(NGS) for epilepsy-related gene-panel was applied to SCN1A mutation-negative patients and their parents. Results In 6 DS families, each consisted of 2 DS patients.Two families had siblings affected, one family involved mother and son, one family involved mother and daughter, one had monozygotic twins affected and one had dizygotic twins involved.SCN1A mutations were identified in 5 DS families(R101Q, R377X, L390P, F1486L, R1245X). Among the 5 DS families with SCN1A mutations, 3 families were identified as inherited heterozygous mutations, and phenotypes of the transmitting parents were DS or febrile seizure plus(FS+ ). While 2 families were highly suspected of parental mosaicism from the results of Sanger sequencing, and the transmitting parents had no history of febrile and epileptic seizures.No SCN1A and other DS-related gene mutation that had been reported was found in the remaining family and the phenotype of parents were normal. Conclusions The affected members of familial DS could be exhibited as one parent and child affected, or sibling pairs, monozygotic or dizygotic twins involved.The majority of familial DS carried SCN1A mutations, while others might carry other DS-causing gene mutation.The mutations of familial DS patients were inherited from one parent, including a mosaic transmitting parent.The phenotypes of the parent carrying SCN1A mutation could be DS, FS+ or normal. Key words: Dravet syndrome, familial; SCN1A gene; Mosaicism

Clinical features and gene mutations in epilepsy of infancy with migrating focal seizures

Objective: To summarize the clinical features and gene mutations of epilepsy of infancy with migrating focal seizures (EIMFS). Method: Clinical features and electroencephalograms(EEG)of 9 patients with EIMFS of Peking University First Hospital from May 2015 to January 2016 were analyzed. Candidate gene mutations were screened by next generation sequencing. Result: Among the 9 patients, 3 were males and 6 were females. Two patients had family history. Seizure onset age was 2 days to 3 months after birth (median age 35 days). Migrating focal seizure was presented. Seizures manifested as eyes and(or)head deviation, involuntary blinking, swallowing, trembling or stiffness of limbs, hand clenching, flushing and cyanosis of lips, etc. Four patients had a history of status epilepticus. All 9 patients had psychomotor delay. EEG of all patients presented relatively slow background; during interictal phase, there were multi-focal epileptic discharges, which dominated one hemisphere or brain region; seizures were recorded in all 9 cases, which manifested eyes or(and)head deviation, stiffening or trembling of limbs, lip smacking, etc. Corresponding EEG showed low-medium-amplitude fast waves that originated from some brain regions and migrated to other regions. Cranial magnetic resonance imaging (MRI) was abnormal in 4 cases, which predominantly showed white matter dysplasia and enlargement of subarachnoid spaces. Two cases carried heterozygous missense mutations of SCN1A gene, while 3 cases carried heterozygous missense mutations of KCNT1 gene, all of which were de novo. One case carried compound heterozygous mutation of TBC1D24 gene(p.Gln207*, p. Ala289Va). Gene mutation was not found in 3 cases. All patients used multiple antiepileptic drugs (AED) and their seizures were not controlled. Follow-up ranged from 2 months to 5 years and 8 months, during which 4 were found dead. Two were lost to follow-up. Conclusion: EIMFS is clinically characterized by early onset, which is usually within 3 months after birth, migrating focal seizures, psychomotor delay, bad response to AED and high death rate. The interictal EEG showed multi-focal discharges, while ictal EEG shows migrating multifocal discharges. Genetic analysis can assist in diagnosis and genetic counseling.

Analysis of SCN5A Gene Variants in East Slovak Patients with Cardiomyopathy.

Mutations in ion channels genes are potential cause of cardiomyopathy. The SCN5A gene (sodium channel, voltage gated, type V alpha subunit gene; 3p21) belongs to the family of cardiac sodium channel genes. Mutations in SCN5A gene lead to decreased Na+ current and ion unbalance. The SCN5A gene mutations are found in approximately 2% of patients with dilated cardiomyopathy (DCM), and they may be potential phenotype modifiers in hypertrophic cardiomyopathy (HCM). The role of SCN5A gene mutations in cardiomyopathy is not fully elucidated. Three selected exons (12, 20, and 21) of the SCN5A gene in the cohort of 58 East Slovak patients with dilated and HCM were analyzed by the Sanger sequencing method in order to detect etiopathogenic mutations associated with dilated and HCM. The mutation screening of three selected exons of SCN5A gene in the cohort of 27 DCM, 12 HCM patients, and 16 controls identified 10 missense genetic variants. Three of them (T1247I, A1260D, and G1262S), all in exon 21 of the SCN5A gene, were potentially damaging and disease-causing variants. Data from this study demonstrate that SCN5A gene variants have important role in the etiopathogenesis of dilated and HCM.

A novel mutation of α-galactosidase A gene causes Fabry disease mimicking primary erythromelalgia in a Chinese family

Purpose: Fabry disease is an X-linked genetic disorder caused by the mutations of α-galactosidase A (GLA, MIM 300644) gene presenting with various clinical symptoms including small-fiber peripheral neuropathy and limb burning pain. Here, we reported a Chinese pedigree with the initial diagnosis of primary erythromelalgia in an autosomal dominant (AD)-inherited pattern. Methods: Mutation analysis of SCN9A and GLA genes by direct sequencing and functional analysis of a novel mutation of GLA in cells were performed. Results: Our data did not show any pathological mutations in SCN9A gene; however, a novel missense mutation c.139T>C (p.W47R) of GLA was identified in a male proband as well as two female carriers in this family. Enzyme assay of α-galactosidase A activity showed deficient enzyme activity in male patients and female carriers, further confirming the diagnosis of Fabry disease. Finally, a functional analysis indicated that the replacement of the 47th amino acid tryptophan (W47) with arginine (W47R) or glycine (W47G) led to reduced activity of α-galactosidase A in 293T cells. Therefore, these findings demonstrated that the novel mutation p.W47R of GLA is the cause of Fabry disease. Conclusions: Because Fabry disease and primary erythromelalgia share similar symptoms, it is a good strategy for clinical physicians to perform genetic mutation screenings on both SCN9A and GLA genes in those patients with limb burning pain but without a clear inheritant pattern.

SCN1A gene variation and related epilepsy syndrome

Among the genes involved in epilepsy, the SCN1A gene represents one of the most commonly mutated human epilepsy genes, refers to be as super culprit gene, SCN1A mutations cause epilepsy phenotype heterogeneity, diversity of clinical manifestations, the light performance of febrile seizures, it shows severe infant severe myoclonic epilepsy.By retrieving SCN1A in gene mutation database, about 900 gene mutatation are associated with epilepsy syndrome.This article reviews the importance of SCN1A gene mutation associates with epilepsy syndrome, and the importance of genetic screening SCN1A. Key words: SCN1A gene; Gene mutation; Epilepsy

Prognostic Challenges of SCN1A Genetic Mutations: Report on Two Children with Mild Features

Mutations in the gene encoding the α-1 subunit of the voltage-gated sodium channel (SCN1A) are associated with variable but usually severe clinical course, both for the epileptic seizures and the cognitive impairment. The purpose of the present study was to retrospectively review two patients affected by seizures and two different types of SCN1A gene mutations (microdeletion and point mutation). The children (a 4-year-old girl and a 3-year-old boy) were affected by generalized tonic–clonic seizures and myoclonic jerks plus unilateral seizures, respectively. Genetic analyses showed, in the girl, the presence of a 4 MB deletion involving SCN1A and four other genes, and a point mutation in the boy. Both the patients showed a mild clinical course, with a good pharmacological control of the crises and sufficient scholastic performances. At present, the role of the combination of SCN1A mutations and the related clinical manifestations is not very clear. Prognostic counseling is particularly challenging given that, in many cases, the clinical course of these patients is independent of the genotype and its severity is difficult to predict.

Paramyotonia congenita caused by a novel mutation of SCN4A gene in a Chinese family

To detect SCN4A gene mutation in a pedigree with paramyotonia congenita in order to facilitate genetic counseling and assisted reproduction. Clinical data of the family was collected. DNA was extracted from peripheral blood samples. Potential mutation of the SCN4A gene was screened using PCR-Sanger sequencing. Potential mutation was detected in 3 affected relatives, 4 unaffected relatives and 100 unrelated healthy controls. Bioinformatics software was used to predict the effect of mutation on the protein function and conservation of the sequence at the mutation site across various species. A novel missense mutation c.4427T>C (p.Met1476Thr) was detected in the exon 24 of the SCN4A gene in the proband and other 3 affected relatives, but not in 4 unaffected relatives and 100 unrelated controls. Bioinformatic analysis indicated that the codon is highly conserved across various species, and that the mutation has caused damage to the structure and function of SCN4A protein. The c.4427 T>C (p.Met1476Thr) mutation of the SCN4A gene may contribute to the paramyotonia congenita. Detection of SCN4A gene mutation is an effective method for the diagnosis of paramyotonic congenita.

A New Electrocardiographic Marker of Sudden Death in Brugada Syndrome: The S-Wave in Lead I

BackgroundRisk stratification in asymptomatic patients remains by far the most important yet unresolved clinical problem in the Brugada syndrome (BrS). ObjectivesThis study sought to analyze the usefulness of electrocardiographic parameters as markers of sudden cardiac death (SCD) in BrS. MethodsThis study analyzed data from 347 consecutive patients (78.4% male; mean age 45 ± 13.1 years) with spontaneous type 1 BrS by ECG parameters but with no history of cardiac arrest (including 91.1% asymptomatic at presentation, 5.2% with a history of atrial fibrillation [AF], and 4% with a history of arrhythmic syncope). Electrocardiographic characteristics at the first clinic visit were analyzed to predict ventricular fibrillation (VF)/SCD during follow-up. ResultsDuring the follow-up (48 ± 38 months), 276 (79.5%) patients remained asymptomatic, 39 (11.2%) developed syncope, and 32 (9.2%) developed VF/SCD. Patients who developed VF/SCD had a lower prevalence of SCN5A gene mutations (p = 0.009) and a higher prevalence of positive electrophysiological study results (p < 0.0001), a family history of SCD (p = 0.03), and AF (p < 0.0001). The most powerful marker for VF/SCD was a significant S-wave (≥0.1 mV and/or ≥40 ms) in lead I. In the multivariate analysis, the duration of S-wave in lead I ≥40 ms (hazard ratio: 39.1) and AF (hazard ratio: 3.7) were independent predictors of VF/SCD during follow-up. Electroanatomic mapping in 12 patients showed an endocardial activation time significantly longer in patients with an S-wave in lead I, mostly because of a significant delay in the anterolateral right ventricular outflow tract. ConclusionsThe presence of a wide and/or large S-wave in lead I was a powerful predictor of life-threatening ventricular arrhythmias in patients with BrS and no history of cardiac arrest at presentation. However, the prognostic value of a significant S-wave in lead I should be confirmed by larger studies and by an independent confirmation cohort of healthy subjects.

Biophysical Characterization of Two Nav1.4 Mutations Identified in Patients with Cold-Induced Myotonia and Periodic Paralysis

Mutations in SCN4A gene encoding Nav1.4, the skeletal muscle voltage-gated Na channel underlie several skeletal muscle ion channelopathies whose two major phenotypes include enhanced excitability (myotonia), transient loss of excitability (periodic paralysis), a fluctuation between these two conditions or severe loss of function (myasthenia).Here, we report two novel dominant SCN4A missense mutations: R1451C, found in a patient with paramyotonia congenita (PMC) exhibiting cold-induced myotonia, and R1451L found in a patient diagnosed with periodic paralysis. These mutations are located in the transmembrane segment S4 of DIV domain.To elucidate the mechanism underlying the phenotypes caused by R1451C and R1451L, we used the whole-cell patch-clamp technique to study tsA201 cells expressing WT, R1451C or R1451L channels.Our results show that both mutations impaired fast inactivation kinetics at room temperature, with R1451L being the most affected. However, R1451C exhibited a unique temperature-dependent alteration of the fast inactivation kinetics that can explain the occurrence of myotonia in cold environment. Slow inactivation was assessed for both mutants, and revealed that the recovery from slow inactivation was only slowed for R1451L. This could explain the periodic paralysis phenotype of the patient. Homology modeling and in silico mutagenesis of R1451C and R1451L in the resting state based on a previous model of the channel was also used to probe the potential structural differences between these two mutations. The model revealed a reorganization of the hydrogen bonds between S4 and other segments in both mutations.We conclude from our investigation that the nature of the mutation is accountable for the clinical differences revealed in the patient carriers.

SCN5A(K817E), a novel Brugada syndrome–associated mutation that alters the activation gating of NaV1.5 channel

Brugada syndrome (BrS) is an inherited lethal arrhythmic disorder characterized by syncope and sudden cardiac death from ventricular tachyarrhythmias. Here we identified a novel K817E mutation of SCN5A gene in a man with type 1 BrS electrocardiogram pattern using next-generation sequencing targeted for 73 cardiac disorder-related genes. SCN5A encodes the α-subunit of NaV1.5 voltage-gated Na(+) channel, and some of its mutations are linked to BrS. The proband had no mutation in any of the other arrhythmia-related genes sequenced. We investigated whether the K817E mutation causes a functional change of NaV1.5 channel responsible for the BrS phenotype. We compared the electrophysiological properties of the whole-cell currents mediated by wild-type and mutant channels heterologously expressed in human embryonic kidney 293 cells by using a voltage-clamp technique. The K817E mutation reduced the Na(+) current density by 39.0%-91.4% at membrane potentials from -55 to -5 mV. This reduction resulted from a ~24-mV positive shift in the voltage dependence of activation. The mutation also decelerated recovery from both fast and intermediate inactivation, whereas it had little effect on the cell surface expression, single-channel conductance, voltage-dependence of fast inactivation, entry into intermediate inactivation, use-dependent loss of channel availability, or closed-state inactivation. The K817E mutation of SCN5A gene leads to loss of function of NaV1.5 channel and may underlie the BrS phenotype of the proband.

Epidural Analgesia with Ropivacaine during Labour in a Patient with a SCN5A Gene Mutation.

SCN5A gene mutations can lead to ion channel defects which can cause cardiac conduction disturbances. In the presence of specific ECG characteristics, this mutation is called Brugada syndrome. Many drugs are associated with adverse events, making anesthesia in patients with SCN5A gene mutations or Brugada syndrome challenging. In this case report, we describe a pregnant patient with this mutation who received epidural analgesia using low dose ropivacaine and sufentanil during labour.

The diagnosis of idiopathic epilepsy in children based on the algorithm of molecular-genetic studies

To study mutations and polymorphisms in the sodium channels genes, determining the development of idiopathic epilepsy (IE). The study of SCN1A gene by direct Sanger sequencing in 53 patients and targeted resequencing of the regions of 34 genes in 40 patients with different clinical forms of IE was performed. Seven mutations (c.3022G>T, c.3637C>T, c.1144G>T, c.80G>C, c.1603C>T, c.2427G>A and c.1131A>C) were detected among 53 patients by direct Sanger sequencing of SCN1A gene. The mutations of SCN1A gene (2 - nonsense mutation, 5 - missense mutation) were identified in 7/40 (17.5%) patients with epilepsy using high-performance sequencing, Mutations in sodium channel genes encoding other subunits: SCN1B, SCN2A, SCN9A were identified in 6 patients. As epileptic encephalopathy is polygenic, it is important to conduct genetic testing of more genes (primarily sodium channel genes - SCN1B, SCN2A, SCN9A etc.) using special gene panels to find the molecular defect in DNA.

Genetic analysis of Iranian family with hereditary cardiac arrhythmias by next generation sequencing.

Background:Cardiac arrhythmias are responsible for several cases of syncope and sudden cardiac death annually worldwide. Due to overlapping clinical symptoms in some cardiac arrhythmias genetic studies would help to confirm the primary clinical diagnosis made on the basis of solely clinical findings. In addition clinical management of the patient, family screening and provide appropriate counseling and risk assessment for the family members are other advantages of genetic study.Materials and Methods:Totally nine patients from a family included in this study. The primary diagnosis on the basis of clinical findings was second-degree atrioventricular (AV) block for this family. Mutation in SCN5A gene is frequently reported for second-degree AV block and hence the gene was analyzed using whole gene sequencing but no mutation was detected. Subsequently, the samples were subjected to customized Ampliseq 77 gene panel using next generation sequencing to detect the underlying molecular defects.Results:We found c. 5570T>A missense mutation in ANK2 gene for this family. Based on the Online Mendelian Inheritance in Man, ANK2 gene and the mutation detected correspond to long QT syndrome type 4.Conclusion:This mutation, although already known in other populations, but is reported for the first time in Iranian patients with cardiac arrhythmias. As the case with this family, genetic analysis of patients with cardiac arrhythmias would be helpful in reassessment of clinical diagnosis and therefore would help for patients’ management and in some cases re-evaluation of ongoing treatment may be needed.

Brugada syndrome genetic testing: A reliable sanger sequencing protocol

The Brugada syndrome (BrS) is a potentially lethal, inheritable arrhythmia syndrome affecting about 5 in 10,000 people worldwide. This cardiac disorder, triggered by mutations in SCN5A gene (encoding for cardiac sodium channels), results in changes in the onset or propagation of cardiac action potential that can generate arrhythmias, potentially fatal. In the last few years, the genetic studies are performed with next generation sequencing (NGS), obtaining global genomic information. However, this strategy requires capillary electrophoresis data validations. In this study, we developed and optimized a Sanger sequencing workflow for SCN5A gene exons.

G.P.78 - A Finnish mutation in SCN4A gene causes predominantly myalgic phenotype

G.P.78 - A Finnish mutation in SCN4A gene causes predominantly myalgic phenotype

AB026. SCN1A mutational analysis in 20 Vietnamese children with Dravet syndrome

Background Dravet syndrome is one of the most catastrophic types of epilepsy in infants. It is found that 70-80% of cases of Dravet syndrome are caused by mutations in SCN1A, the gene encoding alpha-1 subunit of the sodium channel. Mutations of the SCN1A gene have an autosomal dominant inheritance pattern. To date, over 1,000 SCN1A mutations have been reported all over the world, however, no SCN1A mutation studies have been performed in the Vietnamese population, and genetic characteristics of Vietnamese Dravet patients are not yet clear. In this study, we analyzed SCN1A gene in 20 Vietnamese patients with clinical features of Dravet syndrome at Children’s Hospital 2, Ho Chi Minh City, Vietnam.