Identification of a novel Scn3b mutation in a Chinese Brugada syndrome pedigree: implications for Nav1.5 electrophysiological properties and intracellular distribution of Nav1.5 and Navβ3
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SUBMITTER: Fan J
PROVIDER: S-EPMC10916001 | biostudies-literature | 2024 Jan
REPOSITORIES: biostudies-literature
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Project description:Background and aimsPatients suffering from Brugada syndrome (BrS) are predisposed to life-threatening cardiac arrhythmias. Diagnosis is challenging due to the elusive electrocardiographic (ECG) signature that often requires unconventional ECG lead placement and drug challenges to be detected. Although NaV1.5 sodium channel dysfunction is a recognized pathophysiological mechanism in BrS, only 25% of patients have detectable SCN5A variants. Given the emerging role of autoimmunity in cardiac ion channel function, this study explores the presence and potential impact of anti-NaV1.5 autoantibodies in BrS patients.MethodsUsing engineered HEK293A cells expressing recombinant NaV1.5 protein, plasma from 50 BrS patients and 50 controls was screened for anti-NaV1.5 autoantibodies via western blot, with specificity confirmed by immunoprecipitation and immunofluorescence. The impact of these autoantibodies on sodium current density and their pathophysiological effects were assessed in cellular models and through plasma injection in wild-type mice.ResultsAnti-NaV1.5 autoantibodies were detected in 90% of BrS patients vs. 6% of controls, yielding a diagnostic area under the curve of .92, with 94% specificity and 90% sensitivity. These findings were consistent across varying patient demographics and independent of SCN5A mutation status. Electrophysiological studies demonstrated a significant reduction specifically in sodium current density. Notably, mice injected with BrS plasma showed Brugada-like ECG abnormalities, supporting the pathogenic role of these autoantibodies.ConclusionsThe study demonstrates the presence of anti-NaV1.5 autoantibodies in the majority of BrS patients, suggesting an immunopathogenic component of the syndrome beyond genetic predispositions. These autoantibodies, which could serve as additional diagnostic markers, also prompt reconsideration of the underlying mechanisms of BrS, as evidenced by their role in inducing the ECG signature of the syndrome in wild-type mice. These findings encourage a more comprehensive diagnostic approach and point to new avenues for therapeutic research.
| S-EPMC11491155 | biostudies-literature
Project description:We identify a human mutation (E1053K) in the ankyrin-binding motif of Na(v)1.5 that is associated with Brugada syndrome, a fatal cardiac arrhythmia caused by altered function of Na(v)1.5. The E1053K mutation abolishes binding of Na(v)1.5 to ankyrin-G, and also prevents accumulation of Na(v)1.5 at cell surface sites in ventricular cardiomyocytes. Ankyrin-G and Na(v)1.5 are both localized at intercalated disc and T-tubule membranes in cardiomyocytes, and Na(v)1.5 coimmunoprecipitates with 190-kDa ankyrin-G from detergent-soluble lysates from rat heart. These data suggest that Na(v)1.5 associates with ankyrin-G and that ankyrin-G is required for Na(v)1.5 localization at excitable membranes in cardiomyocytes. Together with previous work in neurons, these results in cardiomyocytes suggest that ankyrin-G participates in a common pathway for localization of voltage-gated Na(v) channels at sites of function in multiple excitable cell types.
| S-EPMC536011 | biostudies-literature
Project description:Brugada syndrome (BrS) is an inherited arrhythmogenic syndrome leading to sudden cardiac death, partially associated with autosomal dominant mutations in SCN5A, which encodes the cardiac sodium channel alpha-subunit (Nav1.5). To date some SCN5A mutations related with BrS have been identified in voltage sensor of Nav1.5. Here, we describe a dominant missense mutation (R1629Q) localized in the fourth segment of domain IV region (DIV-S4) in a Chinese Han family. The mutation was identified by direct sequencing of SCN5A from the proband's DNA. Co-expression of Wild-type (WT) or R1629Q Nav1.5 channel and hβ1 subunit were achieved in human embryonic kidney cells by transient transfection. Sodium currents were recorded using whole cell patch-clamp protocols. No significant changes between WT and R1629Q currents were observed in current density or steady-state activation. However, hyperpolarized shift of steady-state inactivation curve was identified in cells expressing R1629Q channel (WT: V1/2 = -81.1 ± 1.3 mV, n = 13; R1629Q: V1/2 = -101.7 ± 1.2 mV, n = 18). Moreover, R1629Q channel showed enhanced intermediate inactivation and prolonged recovery time from inactivation. In summary, this study reveals that R1629Q mutation causes a distinct loss-of-function of the channel due to alter its electrophysiological characteristics, and facilitates our understanding of biophysical mechanisms of BrS.
| S-EPMC3805610 | biostudies-literature
Project description:Cardiac Nav1.5 and Kir2.1-2.3 channels generate Na (INa) and inward rectifier K (IK1) currents, respectively. The functional INa and IK1 interplay is reinforced by the positive and reciprocal modulation between Nav15 and Kir2.1/2.2 channels to strengthen the control of ventricular excitability. Loss-of-function mutations in the SCN5A gene, which encodes Nav1.5 channels, underlie several inherited arrhythmogenic syndromes, including Brugada syndrome (BrS). We investigated whether the presence of BrS-associated mutations alters IK1 density concomitantly with INa density. Results obtained using mouse models of SCN5A haploinsufficiency, and the overexpression of native and mutated Nav1.5 channels in expression systems - rat ventricular cardiomyocytes and human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) - demonstrated that endoplasmic reticulum (ER) trafficking-defective Nav1.5 channels significantly decreased IK1, since they did not positively modulate Kir2.1/2.2 channels. Moreover, Golgi trafficking-defective Nav1.5 mutants produced a dominant negative effect on Kir2.1/2.2 and thus an additional IK1 reduction. Moreover, ER trafficking-defective Nav1.5 channels can be partially rescued by Kir2.1/2.2 channels through an unconventional secretory route that involves Golgi reassembly stacking proteins (GRASPs). Therefore, cardiac excitability would be greatly affected in subjects harboring Nav1.5 mutations with Golgi trafficking defects, since these mutants can concomitantly trap Kir2.1/2.2 channels, thus unexpectedly decreasing IK1 in addition to INa.
| S-EPMC6237221 | biostudies-literature
Project description:SCN5A is abundant in heart and has a major role in INa. Loss-of-function mutation in SCN5A results in Brugada syndrome (BrS), which causes sudden death in adults. It remains unclear why disease phenotype does not manifest in the young even though mutated SCN5A is expressed in the young. The aim of the present study is to elucidate the timing of the disease manifestation in BrS. A gain-of-function mutation in SCN5A also results in Long QT syndrome type 3 (LQTS3), leading to sudden death in the young. Induced pluripotent stem cells (iPSCs) were generated from a patient with a mixed phenotype of LQTS3 and BrS with the E1784K SCN5A mutation. Here we show that electrophysiological analysis revealed that LQTS3/BrS iPSC-derived cardiomyocytes recapitulate the phenotype of LQTS3 but not BrS. Each β-subunit of the sodium channel is differentially expressed in embryonic and adult hearts. SCN3B is highly expressed in embryonic hearts and iPSC-derived cardiomyocytes. A heterologous expression system revealed that INa of mutated SCN5A is decreased and SCN3B augmented INa of mutated SCN5A. Knockdown of SCN3B in LQTS3/BrS iPSC-derived cardiomyocytes successfully unmasked the phenotype of BrS. Isogenic control of LQTS3/BrS (corrected-LQTS3/BrS) iPSC-derived cardiomyocytes gained the normal electrophysiological properties.
| S-EPMC5039759 | biostudies-literature
Project description:Mutations in the long-range limb-specific cis-regulator (ZRS) could cause ectopic shh gene expression and are responsible for preaxial polydactyly (PPD). In this study, we analyzed a large Chinese isolated autosomal dominant PPD pedigree. By fine mapping and haplotype construction, we located the linked region to a 1.7 cM interval between flanking markers D7S2465 and D7S2423 of chromosome 7q36. We directly sequenced the candidate loci in this linked region, including the coding regions of the five genes (HLXB9, LMBR1, NOM1, RNF32 and C7orf13), the regulatory element (ZRS) of shh, the whole intron 5 of LMBR1 which contained the ZRS, and 18 conserved noncoding sequences (CNSs). Interestingly, no pathogenic mutation was identified. By using real-time quantitative PCR (qPCR), we also excluded the ZRS duplication in this pedigree. Our results indicate that, at least, it is not the mutation in a functional gene, CNS region or duplication of ZRS that cause the phenotype of this pedigree. The etiology of this PPD family still remains unclear and the question whether another limb-specific regulatory element of shh gene exists in the noncoding region in this 1.7 cM interval remains open for future research.
| S-EPMC2986254 | biostudies-literature
Project description:BackgroundHashimoto's thyroiditis is a complex autoimmune thyroid disease, the onset of which is associated with environmental exposures and specific susceptibility genes. Its incidence in females is higher than its incidence in males. Thus far, although some susceptibility loci have been elaborated, including PTPN22, FOXP3, and CD25, the aetiology and pathogenesis of Hashimoto's thyroiditis remains unclear.MethodsFour affected members from a Chinese family with Hashimoto's thyroiditis were selected for whole-exome sequencing. Missense, nonsense, frameshift, or splicing-site variants shared by all affected members were identified after frequency filtering against public and internal exome databases. Segregation analysis was performed by Sanger sequencing among all members with available DNA.ResultsWe identified a missense mutation in PTPN22 (NM_015967.5; c. 77A > G; p.Asn26Ser) using whole-exome sequencing. PTPN22 is a known susceptibility gene associated with increased risks of multiple autoimmune diseases. Cosegregation analysis confirmed that all patients in this family, all of whom were female, carried the mutation. All public and private databases showed that the missense mutation was extremely rare.ConclusionsWe found a missense mutation in PTPN22 in a Chinese HT pedigree using whole-exome sequencing. Our study, for the first time, linked a rare variant of PTPN22 to Hashimoto's thyroiditis, providing further evidence of the disease-causing or susceptibility role of PTPN22 in autoimmune thyroid disease. Functional studies regarding the effects of this variant on thyroid autoimmunity and thyroid function are warranted.
| S-EPMC6211547 | biostudies-literature
Project description:AimTo analyze phenotype and genotype of a Chinese pedigree with Avellino corneal dystrophy (ACD).MethodsComplete ophthalmic examinations were performed on all the family members. Exons of TGFBI were amplified by polymerase chain reaction, sequenced, and compared with a reference database.ResultsA single heterozygous G>A (R124H) point mutation was identified in exon 4 of TGFBI in three affected members and two unaffected children who were offsprings of the affected members, but not in the other family members.ConclusionMutation R124H in TGFBI was identified in this pedigree and appeared to be the disease causing mutation. Atypical phenotype and low penetrance was observed in this pedigree.
| S-EPMC3340809 | biostudies-literature
Project description:BackgroundIn the initiation and maintenance of arrhythmia, inflammatory processes play an important role. IL-2 is a pro-inflammatory factor which is associated with the morbidity of arrhythmias, however, how IL-2 affects the cardiac electrophysiology is still unknown.MethodsIn the present study, we observed the effect of IL-2 by qRT-PCR on the transcription of ion channel genes including SCN2A, SCN3A, SCN4A, SCN5A, SCN9A, SCN10A, SCN1B, SCN2B, SCN3B, KCNN1, KCNJ5, KCNE1, KCNE2, KCNE3, KCND3, KCNQ1, KCNA5, KCNH2 and CACNA1C. Western blot assays and electrophysiological studies were performed to demonstrate the effect of IL-2 on the translation of SCN3B/scn3b and sodium currents.ResultsThe results showed that transcriptional level of SCN3B was up-regulated significantly in Hela cells (3.28-fold, p = 0.022 compared with the control group). Consistent results were verified in HL-1 cells (3.73-fold, p = 0.012 compared with the control group). The result of electrophysiological studies showed that sodium current density increased significantly in cells which treated by IL-2 and the effect of IL-2 on sodium currents was independent of SCN3B (1.4 folds, p = 0.023). Western blot analysis showed IL-2 lead to the significantly increasing of p53 and scn3b (2.1 folds, p = 0.021 for p53; 3.1 folds, p = 0.023 for scn3b) in HL-1 cells. Consistent results were showed in HEK293 cells using qRT-PCR analysis (1.43 folds for P53, p = 0.022; 1.57 folds for SCN3B, p = 0.05).ConclusionsThe present study suggested that IL-2, may play role in the arrhythmia by regulating the expression of SCN3B and sodium current density.
| S-EPMC4700781 | biostudies-literature
Project description:PurposeTo analyze transforming growth factor beta-induced (TGFBI) gene mutations in a Chinese pedigree with Reis-Bücklers dystrophy (RBCD).MethodsIn a four-generation Chinese family with Reis-Bücklers dystrophy, six members were patients and the rest were unaffected. All members of the family underwent complete ophthalmologic examinations. Exons of TGFBI were amplified by polymerase chain reaction, sequenced, and compared with a reference database. The sequencing results were reconfirmed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).ResultsA single heterozygous C>T (R124C) point mutation was found in exon 4 of TGFBI in all six members of the pedigree affected with RBCD, but not in the unaffected members.ConclusionsWithin this pedigree, RBCD segregates with the R124C variance, which is a known mutation for lattice corneal dystrophy type I. Therefore, along with G623D and R124L, the R124C mutation in TGFBI is also found to be responsible for RBCD.
| S-EPMC2847680 | biostudies-literature