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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 is a potentially serious channelopathy that usually presents in adulthood and has only rarely been described in infancy. In the absence of metabolic or structural cardiac disease, rapid ventricular tachycardia (>200 bpm) and primary cardiac conduction disease are uncommon in infancy. We hypothesized that infants having rapid ventricular tachycardia and conduction abnormalities and not having structural or metabolic pathogeneses were likely to have mutations in depolarizing current channels. Methods and Results— A retrospective review of all clinical materials from a single institution over a 9-year period from all infants Conclusions— Infants having rapid ventricular tachycardia and conduction abnormalities in the absence of structural or metabolic abnormalities are likely to have disease-causing mutations in cardiac depolarizing channels.

Background: Ion channelopathies are responsible for a number of genetic cardiac arrhythmia syndromes. Recent work demonstrated an association between mutations in CACNA1c and CACNB2b, the genes that encode the α and β subunits of the L-type calcium channel, and the Brugada syndrome (BrS). The mutations previously described all caused a loss of function secondary to a major reduction in peak calcium channel current (I Ca ). In the present study we describe a novel CACNB2b mutation associated with BrS in which loss of function was caused by accelerated inactivation of I Ca . Methods and Results: The proband, a 32 yo male, displayed a saddleback ST segment elevation in the right precordial leads that converted to a coved-type ECG following a procainamide challenge. His EP study was positive with double extrastimuli inducing polymorphic VT/VF. He was also diagnosed with vasovagal syncope. Genomic DNA was isolated from blood lymphocytes. All exons and intron borders of 12 ion channel genes were amplified and sequenced. The only mutation uncovered was a missense mutation (T11I) in CACNB2b. The effect of this mutation was studied by expression of WT or T11I CACNB2b in TSA201 cells co-transfected with WT CANCA1c and CACNA2d. Patch clamp analysis showed no difference in I Ca density between WT and T11I (17.9±1.8 vs 22.5±4.3 pA/pF, respectively at +20mV). Similarly, steady-state inactivation and channel recovery was not different between WT and T11I mutant channels. However, both the fast and slow decay of I Ca produced by T11I mutant were significantly faster compared to WT at potentials between −10 to +30 mV, suggesting a reduction in depolarizing current during the course of an action potential. Application of action potential voltage clamp pulses confirmed that T11I total charge was reduced by 42±2.3% compared to WT (p Conclusion: We report the first Brugada syndrome mutation in CaCNB2b resulting in accelerated inactivation of the L-type calcium channel. The T11I mutation caused a faster decay of cardiac L-type calcium current but did not significantly alter the magnitude of the peak current. Our results suggest that a reduced total charge carried by I Ca during the plateau of the action potential predisposes to the Brugada phenotype.

Background— Cardiac ion channelopathies are responsible for an ever-increasing number and diversity of familial cardiac arrhythmia syndromes. We describe a new clinical entity that consists of an ST-segment elevation in the right precordial ECG leads, a shorter-than-normal QT interval, and a history of sudden cardiac death. Methods and Results— Eighty-two consecutive probands with Brugada syndrome were screened for ion channel gene mutations with direct sequencing. Site-directed mutagenesis was performed, and CHO-K1 cells were cotransfected with cDNAs encoding wild-type or mutant CACNB2b (Ca vβ2b ), CACNA2D1 (Ca vα2δ1 ), and CACNA1C tagged with enhanced yellow fluorescent protein (Ca v 1.2). Whole-cell patch-clamp studies were performed after 48 to 72 hours. Three probands displaying ST-segment elevation and corrected QT intervals ≤360 ms had mutations in genes encoding the cardiac L-type calcium channel. Corrected QT ranged from 330 to 370 ms among probands and clinically affected family members. Rate adaptation of QT interval was reduced. Quinidine normalized the QT interval and prevented stimulation-induced ventricular tachycardia. Genetic and heterologous expression studies revealed loss-of-function missense mutations in CACNA1C (A39V and G490R) and CACNB2 (S481L) encoding the α 1 - and β 2b -subunits of the L-type calcium channel. Confocal microscopy revealed a defect in trafficking of A39V Ca v 1.2 channels but normal trafficking of channels containing G490R Ca v 1.2 or S481L Ca vβ2b -subunits. Conclusions— This is the first report of loss-of-function mutations in genes encoding the cardiac L-type calcium channel to be associated with a familial sudden cardiac death syndrome in which a Brugada syndrome phenotype is combined with shorter-than-normal QT intervals.