Parameters of WT and V1328M channels in the absence of drugs.

<p>Parameters of WT and V1328M channels in the absence of drugs.</p

Use-dependent block of WT and V1328M by pilsicainide.

<p>(A) Superimposed current traces in the absence or presence of 10 μM pilsicainide at pulse number 1, 50 and 100 (P1, P50 and P100). Currents were elicited every 0.5 second by 150 ms pulses to -20 mV from a holding potential of -120 mV. (B) Normalized currents were plotted against the pulse number. (C) Dose-response relationships of the use-dependent block. Fractional block was estimated at pulse #100 in the absence or presence of the drug. The data were fitted with the Hill equation.</p

ECG phenotypes on pilsicainide.

<p>Left panels show baseline ECGs and the right panels show the ECGs after intravenous injection of pilsicainide (0.8 mg/kg).</p

ECG phenotypes.

<p>(A) Type I atrial flutter. (B) PAF.</p

A Novel <i>SCN5A</i> Mutation Associated with Drug Induced Brugada Type ECG

<div><p>Background</p><p>Class IC antiarrhythmic agents may induce acquired forms of Brugada Syndrome. We have identified a novel mutation in <i>SCN5A</i>, the gene that encodes the α-subunit of the human cardiac sodium channel (hNa_v1.5), in a patient who exhibited Brugada- type ECG changes during pharmacotherapy of atrial arrhythmias.</p><p>Objective</p><p>To assess whether the novel mutation p.V1328M can cause drug induced Brugada Syndrome.</p><p>Methods</p><p>Administration of pilsicainide, a class IC antiarrhythmic agent, caused Brugada- type ST elevation in a 66-year-old Japanese male who presented with paroxysmal atrial fibrillation (PAF), type I atrial flutter and inducible ventricular fibrillation (VF) during electrophysiological study. Genetic screening using direct sequencing identified a novel <i>SCN5A</i> variant, p.V1328M. Electrophysiological parameters of WT and p.V1328M and their effects on drug pharmacokinetics were studied using the patch-clamp method.</p><p>Results</p><p>Whole-cell sodium current densities were similar for WT and p.V1328M channels. While p.V1328M mutation did not affect the voltage-dependence of the activation kinetics, it caused a positive shift of voltage-dependent steady-state inactivation by 7 mV. The tonic block in the presence of pilsicainide was similar in WT and p.V1328M, when sodium currents were induced by a low frequency pulse protocol (q15s). On the contrary, p.V1328M mutation enhanced pilsicainide induced use-dependent block at 2 Hz. (<i>Ki</i>: WT, 35.8 μM; V1328M, 19.3 μM).</p><p>Conclusion</p><p>Our study suggests that a subclinical <i>SCN5A</i> mutation, p.V1328M, might predispose individuals harboring it to drug-induced Brugada Syndrome.</p></div

Genetic analysis.

<p>(A) Family tree. The filled square indicates the proband. (B) Abnormal migration pattern identified with DHPLC in the proband. (C) A nucleotide change (3982G>A) identified in the exon 23 of <i>SCN5A</i> (black arrow). (D) Schematic illustration of the SCN5A structure. The red closed circle with the arrowhead indicates the location of p.V1328M mutation.</p

Tonic block of WT and V1328M by pilsicainide.

<p>(A) Representative traces in WT and V1328M in the absence or presence of 50 μM pilsicainide. Currents were elicited every 15 seconds by 150 ms pulses to -20 mV from a holding potential of -120 mV. (B) Dose-response relationship of the tonic block. The data were fitted with the Hill equation: y = 1/[1 + (x/<i>Ki</i>)^<i>n</i>], where y represents the fractional block; x is the concentration of quinidine; <i>Ki</i> is the half-maximal concentration of inhibition; and <i>n</i> is the Hill coefficient. Numbers in parentheses are the number of patches.</p

Top ten most differentially expressed genes and alternatively spliced transcripts in the HLHS-RV group: HLHS-RV vs. Control-RV (Alternatively Spliced Transcripts).

<p>Top ten most differentially expressed genes and alternatively spliced transcripts in the HLHS-RV group: HLHS-RV vs. Control-RV (Alternatively Spliced Transcripts).</p

Principal component plot of normalized gene expression values from microarray analysis of six HLHS (green), five Control-LV (red), and five Control-RV (blue) samples.

<p>Gestational age (in weeks) and postnatal age (in days) of each subject is indicated in parentheses. HLHS-RV samples segregated apart from all Control-RV and Control-LV samples, irrespective of post-natal age and gestational age. Post-natal and gestational age did not appear to result in any particular trend either within the HLHS or the control groups.</p

Splicing Index of the core probe set to indicate individual exon expression in the top three alternatively spiced transcripts in HLHS vs. Control-LV (A) and vs. Control-RV (B).

<p>Purple arrows indicate FDR<0.05 for HLHS vs. indicated control and one-way ANOVA.</p