SCN5A Research Articles

Prevalence and relevance of H558R in the efficacy and toxicity of flecainide in patients with atrial fibrillation: a cohort study.

The SCN5A gene polymorphism histidine-558-to-arginine (H558R) has been associated with atrial fibrillation (AF) and may affect the therapeutic effects of flecainide. This study aimed to assess the prevalence of the H558R polymorphism in a European cohort of patients with AF and examine its association with flecainide's effects on AF recurrence and toxicity. This cohort study included patients diagnosed with AF and prescribed flecainide between 2017 and 2021 in a regional health area. Patients without the polymorphism (H558R-/-) were compared with heterozygous patients (H558R+/-) for a primary outcome of combined 6-month AF recurrence or toxicity. Secondary analyses evaluated the long-term outcomes and compared the prevalence of H558R in the AF cohort to a general population sample (n=3401). A total of 104 patients were enrolled, with 57% H558R-/-, 37% H558R+/- and 6% H558R+/+. The prevalence of the H558R polymorphism was significantly higher in the AF cohort than in the general population (43.27% vs 24.37%, prevalence ratio 1.78, 95% CI 1.41 to 2.23, p<0.01). H558R+/- patients had a significantly lower risk of 6-month AF recurrence or toxicity (p=0.023, risk ratio 0.423, 95% CI 0.189 to 0.947), corresponding to an absolute risk difference of 21.5%. These findings were similar in the multivariable analysis. In long-term follow-up, H558R+/- patients continued to demonstrate a lower risk of AF recurrence or toxicity (p=0.039, HR 0.53, 95% CI 0.276 to 0.999). The H558R polymorphism is more prevalent in patients with AF compared with the general population and its presence is associated with a more favourable response to flecainide treatment.

Allele-Specific Editing of a Dominant SCN8A Epilepsy Variant Protects against Seizures and Lethality in a Murine Model.

Developmental and epileptic encephalopathies (DEEs) can result from dominant, gain of function variants of neuronal ion channels. More than 450 de novo missense variants of the sodium channel gene SCN8A have been identified in individuals with DEE. We studied a mouse model carrying the patient Scn8a variant p.Asn1768Asp. An AAV-PHP.eB virus carrying an allele-specific single guide RNA (sgRNA) was administered by intracerebroventricular injection. Cas9 was provided by an inherited transgene. Allele-specific disruption of the reading frame of the pathogenic transcript generated out-of-frame indels in 1/4 to 1/3 of transcripts throughout the brain. This editing efficiency was sufficient to rescue lethality and seizures. Neuronal hyperexcitability was reduced in cells expressing the virus. The data demonstrate efficient allele-specific editing of a dominant missense variant and support the feasibility of allele-specific therapy for DEE epilepsy. ANN NEUROL 2024;96:958-969.

Two Novel Variants in the CHRNA2 and SCN2A Genes in Italian Patients with Febrile Seizures

Background: Febrile seizures (FSs) are the most common form of epilepsy in children aged between six months and five years. The exact cause is unknown, but several studies have demonstrated the importance of genetic predisposition, with increasing involvement of receptors and ion channels. The present study aims to identify novel pathogenic variants in Italian patients with FSs. Methods: We performed targeted panel sequencing in a cohort of 21 patients with FSs. In silico analysis was performed to predict the pathogenic role of the resulting variants. Results: We found two novel variants segregating in two families with FSs: c.1021C&gt;G (p.Leu341Val) in the CHRNA2 gene and c.140A&gt;G (p.Glu47Gly) in SCN2A. Conclusions: The c.1021C&gt;G (p.Leu341Val) variant leads to a codon change of highly conserved leucine to valine at position 341 and is located in segments M3 of the subunit, which is important for channel gating. The c.140A&gt;G (p.Glu47Gly) variant causes a substitution of glutamic acid with glycine at position 47 of the protein, which is highly conserved across the species. Moreover, it is located in the N-terminal domain, a region commonly affected in ASD, which impacts the inactivation kinetics and voltage dependence of steady-state activation. Further analyses are needed to better explain the role of CHRNA2 and SCN2A in the development of febrile seizures.

Severe Neonatal Episodic Laryngospasm (SNEL) due to Mutation in the SCN4A Gene as a Rare Differential Diagnosis in Paroxysmal Inspiratory Stridor with Cyanosis in Infancy.

Severe Neonatal Episodic Laryngospasm (SNEL) due to Mutation in the SCN4A Gene as a Rare Differential Diagnosis in Paroxysmal Inspiratory Stridor with Cyanosis in Infancy.

The many faces of SCN5A pathogenic variants: from channelopathy to cardiomyopathy.

The SCN5A gene encodes the alpha subunit of the cardiac sodium channel, which plays a fundamental role in the generation and propagation of the action potential in the heart muscle. During the past years our knowledge concerning the function of the cardiac sodium channel and the diseases caused by mutations of the SCN5A gene has grown. Although initially SCN5A pathogenic variants were mainly associated with channelopathies, increasing recent evidence suggests an association with structural heart disease in the form of heart muscle disease. The pathways leading to a cardiomyopathic phenotype remain unclear and require further elucidation. The aim of the present review is to provide a concise summary regarding the mechanisms through which SCN5A pathogenic variants result in heart disease, focusing in cardiomyopathy, highlighting along the way the complex role of the SCN5A gene at the intersection of cardiac excitability and contraction networks.

Epicardial ablation in patients with Brugada syndrome: a single centre experience

Abstract Introduction Brugada syndrome (BrS) is a rare disease associated with an increased risk of ventricular fibrillation (VF), ventricular tachycardia (VT), and sudden cardiac death (SCD). The standard prevention of SCD in patients with BrS is the implantation of an implantable cardioverter-defibrillator (ICD), especially in patients who have previously suffered cardiac arrest or arrhythmogenic syncope. Catheter ablation is an effective method to prevent recurrences of VF/VT in these patients. Purpose Retrospective analysis of the results of catheter ablation by epicardial approach and genetic testing in patients with a diagnosis of BrS and repeated adequate ICD interventions. Methods In 2013-2024, catheter ablation by epicardial approach was performed in our centre in 9 patients diagnosed with Brugada syndrome (mean age 41±6 years, nine males, left ventricular ejection fraction 57±4%). All patients had an ICD implanted for secondary prevention of SCD and presented with adequate ICD therapies (mean 9±11 shocks/patient in the last six months before catheter ablation). Before catheter ablation, two patients were treated with quinidine. Patients underwent cardiogenetic testing by next-generation sequencing of 228 genes. Results Type 1 electrocardiogram (ECG) pattern was present at baseline ECG in four (44%) patients; in five (56%) patients, type 1 was induced after ajmaline administration. Genetic testing was performed in seven patients, and only one patient (14%) was found to have a relevant pathogenic mutation in the SCN5A gene. Prior to ablation, sustained VT/VF could be induced by programmed electrical stimulation in three patients (33%). Epicardial ablation was targeted at areas of abnormal electrograms located over the right ventricular outflow tract. No complications were noted. The mean follow-up period was 25±30 months. In one patient (11%), reablation was required to suppress ventricular arrhythmias successfully. After the last ablation, no recurrence of VT/VF was observed in any patient. Conclusions Epicardial ablation is an effective method that leads to the suppression of ventricular arrhythmias in patients with a diagnosis of BrS and repeated ICD interventions. Despite the malignant arrhythmic phenotype, patients in our cohort had a rather low prevalence of signs associated with a high risk of VT/VF, such as spontaneous ECG pattern of BrS, inducibility of VT/VF during electrical programmed stimulation, or the presence of a causative genetic mutation.

Characterisation of the novel SCN5A-P1891A variant, implicated in left ventricular noncompaction cardiomyopathy in a Finnish family, using human induced pluripotent stem cell-derived cardiomyocytes

Abstract Introduction Left ventricular noncompaction (LVNC) is a heterogenous cardiomyopathy characterised by an extensively trabeculated left ventricle (LV). Several genetic variants that perturb trabeculae compaction, and thus LV maturation, have been reported [1]. However, the precise mechanisms underpinning this have proven contentious with, for example, differentially aberrant cardiomyocyte proliferation implicated in the development of LVNC [2,3]. Purpose In this study, we investigate a novel SCN5A variant, P1891A, which is associated with LVNC in a Finnish family. We ascertain the effects of this variant through the characterisation of variant-carrying human induced pluripotent stem cell-derived cardiomyocytes (P1891A-hiPSC-CMs). Methods We isolated dermal fibroblasts from a symptomatic member of a Finnish family carrying the SCN5A-P1891A variant; derived P1891A-hiPSCs via nucleofection with reprogramming plasmids [4]; and differentiated these into hiPSC-CMs alongside healthy control-hiPSCs. We determined the action potential (AP) and sodium- (INa) and calcium-current (ICa) densities of hiPSC-CMs via patch-clamp. We investigated gene expression in hiPSC-CMs through qPCR and employed Multiple Approaches Combined (MCA) proteomics [5] in SCN5A-transfected HEK293-like cells to elucidate protein-protein interactions (PPI). We subjected hiPSC-CMs to mechanical stretch [6] to examine their stress response and assessed their proliferation capacity via high-content analysis for the percentage of BrdU positive hiPSC-CMs following mitogenic stimulation (5 µM CHIR99021 and 1 µM SB203580). Finally, we ascertained contractile kinetics and apparent contractile force using fibrin hydrogel-based engineered heart tissues (EHTs) [7]. Results The P1891A-hiPSC-CMs demonstrated elevated INa density alongside enhanced arrhythmogenicity relative to healthy control hiPSC-CMs although, AP kinetics and ICa density were unperturbed (Fig. 1). Under baseline conditions, P1891A-hiPSC-CMs exhibited higher SCN5A gene expression and proteomics revealed a reduction in PPI. Baseline proliferation was unchanged; however, aged P1891A-hiPSC-CMs had enhanced proliferative capacity following mitogenic stimulation. Further, the P1891A-hiPSC-CMs displayed impaired tolerance to mechanical stretch as evidenced by upregulated NPPB and ACTA1 expression. In the context of the EHT, P1891A-hiPSC-CMs yielded disparate phenotypes. Whilst a subset compacted fully and yielded weaker contractile parameters relative to healthy control EHTs, the majority of P1891A-hiPSC-CM EHTs failed to fully compact thereby recapitulating the LVNC phenotype (Fig. 2). Conclusions This study presents a unique aetiology of LVNC and links, for the first time, SCN5A mutations with enhanced human cardiomyocyte proliferation. The ability to recapture the noncompaction phenotype in EHTs presents a powerful model for future mechanistic research and drug development.

H558R: a common polymorphism may modify the efficacy and toxicity of flecainide in maintaining sinus rhythm; a cohort study

Abstract Background Certain mutations in the SCN5A gene alter the function of the type V voltage-gated cardiac sodium channel and the therapeutic effect of flecainide.(1) One such mutation, H558R, represents a polymorphism with a high prevalence associated with the development of atrial fibrillation (AF).(2–5) Purpose We aim to determine its relationship with the efficacy and adverse effects of flecainide, as well as describe for the first time its prevalence in a cohort of European patients with AF. Methods We conducted a cohort study collecting data through indirect methods, with the study being blinded to all parties involved except the statistician. Patients prescribed flecainide (dose of 100 mg/12 h) and followed up in our health area (n=450,000 people) between 2017 and 2021 were identified. A primary composite endpoint consisting of initial inefficacy and early toxicity and a secondary combined endpoint of toxicity or inefficacy during follow-up were predefined. Results Out of 104 patients who met the criteria and agreed to participate, 59 (56.4%) did not have the mutation (H558R-/-), 38 (36.5%) were heterozygous (H558R+/-), and 7 (6.7%) were homozygous (H558R+/+). This high prevalence in European patients with AF is significantly higher than that previously reported in healthy individuals (20.4% in Caucasians, 9.2% in Asians).(6) When compared with patients without the mutation, H558R+/- patients had a lower incidence of the primary endpoint (p=0.02, picture 1), with an absolute risk reduction (ARR) of -21.5% (95% confidence interval (CI): -38.4% to -4.6%) primarily due to a lower rate of initial inefficacy (ARR -18.35%, 95% CI: -1.37% to -35.3%), and a trend towards lower early toxicity (ARR -7.36; 95% CI: -19.9 to +5.2%). This difference remained in the multivariate analysis (p=0.03, table 1). Moreover, the H558R+/- genotype was associated with lower toxicity or inefficacy over an average follow-up of 492 days (p=0,04, picture 1), with a hazard ratio of 0.53 (95% CI: 0.27 to 0.999). Conclusions The H558R+/- mutation shows a marked prevalence in a selected sample of patients with AF. Its presence is clinically relevant both in terms of early efficacy or toxicity and during follow-up. If these results are confirmed, it may signify a step towards personalized treatment for patients with AF, not only from the standpoint of efficacy but also safety.Table 1.Picture 1.

Новый электрокардиографический феномен при синдроме удлиненного интервала QT: клиническое наблюдение

Long QT syndrome (LQTS) is a disease with a high risk of sudden death in children. Individual prognosis is based on additional, primarily electrocardiological markers. Authors represent a clinical case of a rare variant of electrocardiographic manifestation of LQTS in children that wasn’t described previously. A 6 y/o female patient with LQTS, had no complaints, no syncope or sudden death familial cases. The molecular genetic study revealed a de novo mutation in the SCN5A gene which is typical for the third molecular genetic variant of LQTS (LQT3). Holter monitoring noted “hyperadaptation” of the QT interval (slope QT/RR 0.37 with a norm of up to 0.24). During night sleep, episodes of combined T-wave and QRS complex alternans (AT/AQRS) were detected. This pattern has not been previously described in patients with LQTS. Possible mechanisms and prognostic value for the revealed ECG pattern, issues of treatment of patients with LQT3 are discussed. Conclusion: combined T-wave and QRS complex alternans (AT/AQRS) is a new, previously undescribed ECG phenomenon in patients with LQTS that is highly likely to increase the risk for cardiac events. Thus the “hyperadaptation” of the QT interval may be one of the electrocardiological signs of LQT3.

Parvalbumin interneuron impairment causes synaptic transmission deficits and seizures in SCN8A developmental and epileptic encephalopathy.

SCN8A developmental and epileptic encephalopathy (DEE) is a severe epilepsy syndrome resulting from mutations in the voltage-gated sodium channel Nav1.6, encoded by the gene SCN8A. Nav1.6 is expressed in excitatory and inhibitory neurons, yet previous studies primarily focus on how SCN8A mutations affect excitatory neurons, with limited studies on the importance of inhibitory interneurons. Parvalbumin (PV) interneurons are a prominent inhibitory interneuron subtype that expresses Nav1.6. To assess PV interneuron function within SCN8A DEE, we used 2 mouse models harboring patient-derived SCN8A gain-of-function variants, Scn8aD/+, where the SCN8A variant N1768D is expressed globally, and Scn8aW/+-PV, where the SCN8A variant R1872W is selectively expressed in PV interneurons. Expression of the R1872W SCN8A variant selectively in PV interneurons led to development of spontaneous seizures and seizure-induced death. Electrophysiology studies showed that Scn8aD/+ and Scn8aW/+-PV interneurons were susceptible to depolarization block and exhibited increased persistent sodium current. Evaluation of synaptic connections between PV interneurons and pyramidal cells showed synaptic transmission deficits in Scn8aD/+ and Scn8aW/+-PV interneurons. Together, our findings indicate that PV interneuron failure via depolarization block along with inhibitory synaptic impairment likely elicits an overall inhibitory reduction in SCN8A DEE, leading to unchecked excitation and ultimately resulting in seizures and seizure-induced death.

The Evolving Landscape of Small Fiber Neuropathy.

Small fiber neuropathy (SFN) belongs to a heterogeneous group of disorders in which thinly myelinated Aδ and unmyelinated C-fibers are primarily affected, leading to neuropathic pain and autonomic symptoms. SFN can be associated with systemic conditions such as diabetes, autoimmune diseases, exposure to drugs and toxins, and infection, with the list of associated diseases continuing to expand. Variants in the SCN9A, SCN10A, and SCN11A genes encoding Nav 1.7, Nav 1.8, and Nav 1.9 sodium channel subunits, as well as in the TRPA1 gene, have been found in SFN patients, expanding the spectrum of underlying conditions and enhancing our understanding of pathophysiological mechanisms. There is also growing interest in immune-mediated forms that could help identify potentially treatable subgroups. According to international criteria, diagnosis is established through clinical examination, the assessment of intraepidermal nerve fiber density, and/or quantitative sensory testing. Autonomic functional tests allow for a better characterization of dysautonomia in SFN, which can be subclinical. Other tests can support the diagnosis. Currently, the management of SFN prioritizes treating the underlying condition, if identified, within a multidisciplinary approach that combines symptomatic pain therapy, lifestyle changes, and biopsychological interventions. Emerging insights from the molecular characterization of SFN channelopathies hold promise for improving diagnosis, potentially leading to the discovery of new drugs and refining trial designs in the future. This article reviews the clinical presentation, diagnostic workup, and advancing knowledge of associated conditions and interventional management of SFN.

A Rare Noncoding Enhancer Variant in SCN5A Contributes to the High Prevalence of Brugada Syndrome in Thailand.

Brugada syndrome (BrS) is a cardiac arrhythmia disorder that causes sudden death in young adults. Rare genetic variants in the SCN5A gene encoding the Nav1.5 sodium channel and common noncoding variants at this locus are robustly associated with the condition. BrS is particularly prevalent in Southeast Asia but the underlying ancestry-specific factors remain largely unknown. Genome sequencing of BrS probands and population-matched controls from Thailand was performed to identify rare noncoding variants at the SCN5A-SCN10A locus that were enriched in patients with BrS. A likely causal variant was prioritized by computational methods and introduced into human induced pluripotent stem cell (hiPSC) lines using CRISPR-Cas9. The effect of the variant on SCN5A expression and Nav1.5 sodium channel current was then assessed in hiPSC-derived cardiomyocytes (hiPSC-CMs). A rare noncoding variant in an SCN5A intronic enhancer region was highly enriched in patients with BrS (detected in 3.9% of cases with a case-control odds ratio of 45.2). The variant affects a nucleotide conserved across all mammalian species and predicted to disrupt a Mef2 transcription factor binding site. Heterozygous introduction of the enhancer variant in hiPSC-CMs caused significantly reduced SCN5A expression from the variant-containing allele and a 30% reduction in Nav1.5-mediated sodium current density compared with isogenic controls, confirming its pathogenicity. Patients with the variant had severe phenotypes, with 89% experiencing cardiac arrest. This is the first example of a functionally validated rare noncoding variant at the SCN5A locus and highlights how genome sequencing in understudied populations can identify novel disease mechanisms. The variant partly explains the increased prevalence of BrS in this region and enables the identification of at-risk variant carriers to reduce the burden of sudden cardiac death in Thailand.

Generation of two induced pluripotent stem cell (iPSC) lines carrying the Brugada Syndrome-associated mutation SCN5A-R282H

Brugada syndrome (BrS) is a cardiac arrhythmia disorder which can lead to sudden cardiac death. It is commonly associated with loss-of-function mutations in the SCN5A gene, encoding the alpha subunit of the sodium voltage-gated channel. We introduced the BrS associated mutation c.845G>A (p.R282H) in the SCN5A gene in a human induced pluripotent stem cell (hiPSC) line. We describe two lines where the mutation is either in the same (cis) or opposite (trans) allele to the common polymorphism c1673A>G (p.H558R). These hiPSC lines provide physiological models to study the role of this mutation and the effect of the polymorphism in BrS.

Clinical Features, Long-Term Prognosis, and Clinical Management of Genotype-Negative Long QT Syndrome Patients.

Approximately 15% to 20% of patients clinically diagnosed with long QT syndrome (LQTS) are genotype-negative (GEN-). Whether they have a different arrhythmic risk or should be managed differently remains unclear, often leading to incomplete treatment. The purpose of this study was to compare clinical aspects of GEN- and genotype-positive (GEN+) LQTS patients. We retrospectively evaluated 832 LQTS patients genetically screened in Japan (n=347) and Italy (n=485), including 698 with a disease-causing variant in the KCNQ1, KCNH2, and SCN5A genes (GEN+), and 134 without variants in these LQTS-related genes (GEN-). At diagnosis, the Japanese patients were more often probands (86% vs 60%), symptomatic (39% vs 18%), and of younger age than the Italian patients; conversely, they used less β-blockers (65% vs 95%), more rarely had a family history (FH) of LQTS (42% vs 73%), and had more cardiac events during follow-up (13% vs 4%) (P< 0.001 for all comparisons). Within the Japanese cohort, the GEN- had more cardiac arrests, used less β-blockers, and had much less FH for LQTS compared their GEN+ counterpart. The Italian cohort was more homogeneous, with just more LQTS FH among the GEN+. QTc shortening (close to 30ms in all groups) during follow-up was similar between Japanese and Italian patients, irrespective of their being GEN+ or GEN-. In both cohorts, during an average follow-up of 6 and 7 years, respectively, GEN+ and GEN- patients showed a comparable clinical outcome. Arrhythmic risk is similar between GEN+ and GEN- LQTS patients; they should be managed and treated in the same way.

Early developmental alterations of CA1 pyramidal cells in Dravet syndrome

Dravet Syndrome (DS) is most often caused by heterozygous loss-of-function mutations in the voltage-gated sodium channel gene SCN1A (Nav1.1), resulting in severe epilepsy and neurodevelopmental impairment thought to be cause by reduced interneuron excitability. However, recent studies in mouse models suggest that interneuron dysfunction alone does not completely explain all the cellular and network impairments seen in DS. Here, we investigated the development of the intrinsic, synaptic, and network properties of CA1 pyramidal cells in a DS model prior to the appearance of overt seizures. We report that CA1 pyramidal cell development is altered by heterozygous reduction of Scn1a, and propose that this is explained by a period of reduced intrinsic excitability in early postnatal life, during which Scn1a is normally expressed in hippocampal pyramidal cells. We also use a novel ex vivo model of homeostatic plasticity to show an instability in homeostatic response during DS epileptogenesis. This study provides evidence for the early effects of Scn1a haploinsufficiency in pyramidal cells in contributing to the pathophysiology of DS.

ParSE-seq: a calibrated multiplexed assay to facilitate the clinical classification of putative splice-altering variants

Interpreting the clinical significance of putative splice-altering variants outside canonical splice sites remains difficult without time-intensive experimental studies. To address this, we introduce Parallel Splice Effect Sequencing (ParSE-seq), a multiplexed assay to quantify variant effects on RNA splicing. We first apply this technique to study hundreds of variants in the arrhythmia-associated gene SCN5A. Variants are studied in ‘minigene’ plasmids with molecular barcodes to allow pooled variant effect quantification. We perform experiments in two cell types, including disease-relevant induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs). The assay strongly separates known control variants from ClinVar, enabling quantitative calibration of the ParSE-seq assay. Using these evidence strengths and experimental data, we reclassify 29 of 34 variants with conflicting interpretations and 11 of 42 variants of uncertain significance. In addition to intronic variants, we show that many synonymous and missense variants disrupted RNA splicing. Two splice-altering variants in the assay also disrupt splicing and sodium current when introduced into iPSC-CMs by CRISPR-Cas9 editing. ParSE-seq provides high-throughput experimental data for RNA-splicing to support precision medicine efforts and can be readily adopted to study other loss-of-function genotype-phenotype relationships.

SCN1A rs6732655A/T polymorphism: Diagnostic and therapeutic insights for drug-resistant epilepsy.

A significant subset of individuals with epilepsy fails to respond to currently available antiepileptic drugs, resulting in heightened mortality rates, psychosocial challenges, and a diminished quality of life. Genetic factors, particularly within the SCN1A gene, and the pro-inflammatory cytokine response is important in intricating the drug resistance in idiopathic epilepsy cases. In this extended study, we determined the correlation of rs6732655A/T single nucleotide polymorphism to understand the causative association of SCN1A gene with epilepsy drug resistance and inflammatory response. To find the correlation of SCN1A gene rs6732655A/T polymorphism with the drug-resistant epilepsy and inflammatory response. The study enrolled 100 age and sex-matched patients of both drug-resistant and drug-responsive epilepsy cases. We analysed the rs6732655A/T polymorphism to study its association and causative role in drug-resistant epilepsy cases using restriction fragment length polymorphism technique. The diagnostic performance of interleukin (IL)-1β, IL-6, and high mobility group box 1 (HMGB1) protein levels was evaluated in conjunction with genotypic outcome receiver operating characteristic analysis. AT and AA genotypes of rs6732655 SCN1A gene polymorphism were associated with higher risk of drug resistance epilepsy. Serum biomarkers IL-6, IL1β and HMGB1 demonstrated diagnostic potential, with cutoff values of 4.63 pg/mL, 59.52 pg/mL and 7.99 ng/mL, respectively, offering valuable tools for epilepsy management. Moreover, specific genotypes (AA and AT) were found to be linked to the elevated levels of IL-1β and IL-6 and potentially reflecting increased oxidative stress and neuro-inflammation in drug-resistant cases supporting the previous reported outcome of high inflammatory markers response in drug resistance epilepsy. SCN1A genotypes AA and AT are linked to higher drug-resistant epilepsy risk. These findings underscore the potential influence of inflammation and genetics on epilepsy treatment resistance.

Modeling Cortical Versus Hippocampal Network Dysfunction in a Human Brain Assembloid Model of Epilepsy and Intellectual Disability.

Neurodevelopmental disorders often impair multiple cognitive domains. For instance, a genetic epilepsy syndrome might cause seizures due to cortical hyperexcitability and present with memory impairments arising from hippocampal dysfunction. This study examines how a single disorder differentially affects distinct brain regions by using human patient iPSC-derived cortical- and hippocampal-ganglionic eminence assembloids to model Developmental and Epileptic Encephalopathy 13 (DEE-13), a condition arising from gain-of-function mutations in the SCN8A gene. While cortical assembloids showed network hyperexcitability akin to epileptogenic tissue, hippocampal assembloids did not, and instead displayed network dysregulation patterns similar to in vivo hippocampal recordings from epilepsy patients. Predictive computational modeling, immunohistochemistry, and single-nucleus RNA sequencing revealed changes in excitatory and inhibitory neuron organization that were specific to hippocampal assembloids. These findings highlight the unique impacts of a single pathogenic variant across brain regions and establish hippocampal assembloids as a platform for studying neurodevelopmental disorders.

Genome-wide association analysis and admixture mapping in a Puerto Rican cohort supports an Alzheimer disease risk locus on chromosome 12.

Hispanic/Latino populations are underrepresented in Alzheimer Disease (AD) genetic studies. Puerto Ricans (PR), a three-way admixed (European, African, and Amerindian) population is the second-largest Hispanic group in the continental US. We aimed to conduct a genome-wide association study (GWAS) and comprehensive analyses to identify novel AD susceptibility loci and characterize known AD genetic risk loci in the PR population. Our study included Whole Genome Sequencing (WGS) and phenotype data from 648 PR individuals (345 AD, 303 cognitively unimpaired). We used a generalized linear-mixed model adjusting for sex, age, population substructure, and genetic relationship matrix. To infer local ancestry, we merged the dataset with the HGDP/1000G reference panel. Subsequently, we conducted univariate admixture mapping (AM) analysis. We identified suggestive signals within the SLC38A1 and SCN8A genes on chromosome 12q13. This region overlaps with an area of linkage of AD in previous studies (12q13) in independent data sets further supporting. Univariate African AM analysis identified one suggestive ancestral block (p = 7.2×10-6) located in the same region. The ancestry-aware approach showed that this region has both European and African ancestral backgrounds and both contributing to the risk in this region. We also replicated 11 different known AD loci -including APOE- identified in mostly European studies, which is likely due to the high European background of the PR population. PR GWAS and AM analysis identified a suggestive AD risk locus on chromosome 12, which includes the SLC38A1 and SCN8A genes. Our findings demonstrate the importance of designing GWAS and ancestry-aware approaches and including underrepresented populations in genetic studies of AD.

SCN2A-linked myelination deficits and synaptic plasticity alterations drive auditory processing disorders in ASD.

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by complex sensory processing deficits. A key unresolved question is how alterations in neural connectivity and communication translate into the behavioral manifestations seen in ASD. Here, we investigate how oligodendrocyte dysfunction alters myelin plasticity and neuronal activity, leading to auditory processing disorder associated with ASD. We focus on the SCN2A gene, an ASD-risk factor, to understand its role in myelination and neural processing within the auditory nervous system. Through transcriptional profiling, we identified alterations in the expression of myelin-associated genes in Scn2a conditional knockout mice, highlighting the cellular consequences engendered by Scn2a deletion in oligodendrocytes. The results reveal a nuanced interplay between oligodendrocytes and axons, where Scn2a deletion causes alterations in the intricate process of myelination. This disruption instigates changes in axonal properties, presynaptic excitability, and synaptic plasticity at the single cell level. Furthermore, oligodendrocyte-specific Scn2a deletion compromises the integrity of neural circuitry within auditory pathways, leading to auditory hypersensitivity. Our findings reveal a novel pathway linking myelin deficits to synaptic activity and sensory abnormalities in ASD.