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Introduction: Cardiac arrhythmias are generally associated with abnormal mutations in ion channel genes. Epilepsy is a disorder of neuronal function, which also involves abnormal channel function. Our Hypothesis: now increasing by demonstration that the etiologies of Brugada syndrome (BrS) and epilepsy may partly overlap. However, only a few genetic studies have addressed a possible link between cardiac and neural channelopathies. Methods: The suspected case and family were underwent thorough medical examination. Fifteen candidate genes were screened for ion channels by direct sequencing. Ion channel variants were cloned by site-directed mutagenesis and studied using patch clamp and confocal microscopy techniques in TSA201 cells. Results: A 36 y/o male with epilepsy showing typical type 1 Brugada pattern ECG during flecainide challenge test and under antiepileptic medication (valproic acid). Cardiac evaluation included a normal echocardiogram and exercise stress test. We identified two mutations (D2130N and A1717G) in CACNA1C and one in KCNE2 (T10M). All mutations are highly conserved. The variants in CACNA1C were located in C terminal and the one in KCNE2 was in N terminal. Functional studies in CACNA1C mutants were co-expressed with CACNB2b and CACNA2D1 . At 0 mV, peak ICa densities were reduced by 85% and 70% in D2130N and A1717G vs. WT respectively. Significant kinetic alterations included a negative shift in V1/2 of inactivation, and positive shift in V1/2 of activation, for D2130N and A1717G, respectively. Confocal study showed D2130N and A1717G conjugated to YFP trafficked normally to the cell membrane. We found a gain-of-function in Ito current when T10M- KCNE2 was co-expressed with KCND3 channels by 55% relative to WT. Conclusion: Our results suggest for the first time that several mutations in CACNA1C leads to a loss of function in ICa and thus can contribute to the development of BrS phenotype. T10M- KCNE2 produces a gain of function in Ito, which further aggravates BrS. Meanwhile, as previously reported, T10M- KCNE2 also produces a loss-of-function of IKr, so it is reasonable to deduce that the mutation is probably responsible for the epilepsy. It once again provides the evidence that anti-epilepsy drug could unmask potential Brugada ECG.

Introduction: Mutations in genes encoding the α ( KCND3) and β ( KCNE3 ) subunits of genes encoding the cardiac transient outward potassium (Ito) have been associated with inherited cardiac arrhythmia syndromes such as Brugada Syndrome (BrS) and Sudden Infant Death Syndromes (SIDS). Hypothesis: Novel genetic variant in DPP10 associated with severe pediatric J Wave Syndrome (JWS), IVF and SIDS. Methods: The proband, a 16 year-old female, presented with atrial fibrillation and atrial septal defect. Subsequently she developed accentuated J waves in all ECG leads leading to repeated episodes of VT/VF (Type 3 ERS). Cilostazol proved effective in quieting VT/VF. She died of an electrical storm at 21 years of old. Genetic screening using Next Gen and Sanger methods uncovered a genetic variant in DPP10 but no variants in any other JWS susceptibility genes. Results: Transversion of thymine for guanine at nucleotide 15 predicted substitution of aspartic acid (D) for glutamine acid (E) at position 5 in exon 1b in the N-terminal of DPP10 (E5D) . The variation E5D was present in 5 unrelated patients with ERS (2), IVF (1) and BrS (3). E5D is highly conserved among species. Wild type (WT) and mutant genes were expressed in TSA201 cells and studied using whole-cell patch-clamp techniques at 37°C. Co-expression of KCND3 + KChIP2 + DPP10 /E5D generated Kv4.3 current density (I to ) 169.9% and 70.6% greater compared with KCND3 + KChIP2 + DPP10 /WT when homozygously and heterozygously expressed, respectively (n=9-12, pto by approximately 50% at +20 mV in E5D channels but less so (20 %) in WT channels. Conclusions: Our results provide, for the first time, evidence in support for the hypothesis that DDP10 is a novel susceptibility gene for life threatening arrhythmias associated with JWS. Our data suggest that DPP10- E5D contributes to the generation of a pathogenic substrate by boosting Ito and that Quinidine and Cilostazol serve as therapeutic options in this setting by reducing I to .

Background— Brugada syndrome, characterized by ST-segment elevation in the right precordial ECG leads and the development of life-threatening ventricular arrhythmias, has been associated with mutations in 6 different genes. We identify and characterize a mutation in a new gene. Methods and Results— A 64-year-old white male displayed a type 1 ST-segment elevation in V1 and V2 during procainamide challenge. Polymerase chain reaction-based direct sequencing was performed using a candidate gene approach. A missense mutation (L10P) was detected in exon 1 of SCN3B , the β3 subunit of the cardiac sodium channel, but not in any other gene known to be associated with Brugada syndrome or in 296 controls. Wild-type (WT) and mutant genes were expressed in TSA201 cells and studied using whole-cell patch-clamp techniques. Coexpression of SCN5A /WT+ SCN1B /WT+ SCN3B /L10P resulted in an 82.6% decrease in peak sodium current density, accelerated inactivation, slowed reactivation, and a −9.6-mV shift of half-inactivation voltage compared with SCN5A /WT+ SCN1B /WT+ SCN3B /WT. Confocal microscopy revealed that SCN5A /WT channels tagged with green fluorescent protein are localized to the cell surface when coexpressed with WT SCN1B and SCN3B but remain trapped in intracellular organelles when coexpressed with SCN1B /WT and SCN3B /L10P. Western blot analysis confirmed the presence of Na V β3 in human ventricular myocardium. Conclusions— Our results provide support for the hypothesis that mutations in SCN3B can lead to loss of transport and functional expression of the hNa v 1.5 protein, leading to reduction in sodium channel current and clinical manifestation of a Brugada phenotype.

Background— The Brugada syndrome, an inherited syndrome associated with a high incidence of sudden cardiac arrest, has been linked to mutations in 4 different genes, leading to a loss of function in sodium and calcium channel activity. Although the transient outward current ( I to ) is thought to play a prominent role in the expression of the syndrome, mutations in I to -related genes have not been identified as yet. Methods and Results— One hundred five probands with the Brugada syndrome were screened for ion channel gene mutations using single-strand conformation polymorphism electrophoresis and direct sequencing. A missense mutation (R99H) in KCNE3 ( MiRP2 ) was detected in 1 proband. The R99H mutation was found 4/4 phenotype-positive and 0/3 phenotype-negative family members. Chinese hamster ovary-K1 cells were cotransfected using wild-type (WT) or mutant KCNE3 and either WT KCND3 or KCNQ1. Whole-cell patch clamp studies were performed after 48 hours. Interactions between Kv4.3 and KCNE3 were analyzed in coimmunoprecipitation experiments in human atrial samples. Cotransfection of R99H- KCNE3 with KCNQ1 produced no alteration in tail current magnitude or kinetics. However, cotransfection of R99H KCNE3 with KCND3 resulted in a significant increase in the I to intensity compared with WT KCNE3 +KCND3. Using tissues isolated from the left atrial appendages of human hearts, we also demonstrate that K v 4.3 and KCNE3 can be coimmunoprecipitated. Conclusions— These results provide definitive evidence for a functional role of KCNE3 in the modulation of I to in the human heart and suggest that mutations in KCNE3 can underlie the development of the Brugada syndrome.