A plasmid containing the green fluorescent protein (GFP) gene (a kind gift from Dr. Kirstine Call? University of Copenhagen, Copenhagen, Denmark) allowed the identification of transfected cells. All experiments were performed 48 hours after transfection.Novel Nav1.5 Pore Mutation I890T Causes BrSNovel Nav1.5 Pore Mutation I890T Causes BrSFigure 
1. Clinical and genetic characterization of the proband and his family. (A) Family pedigree with corresponding ECGs. Open symbols indicate clinically normal subjects and filled symbols mark clinically affected individuals. Plus signs indicate 25033180 the carriers of the mutation I890T and minus signs, non-carriers. The arrow identifies the proband. Basal ECG of the proband and ECGs at the time of the ajmaline test of the family members are presented. (B) Detail of the electropherograms obtained after SCN5A sequence analysis. The arrow indicates the nucleotide position 2669 of SCN5A, where a double peak (T to C heterozygote change, c.2669 T.C) was identified in the proband’s DNA. doi:10.1371/journal.pone.0053220.gdetected with the SuperSignal West Femto Chemiluminiscent substrate (Pierce). A mouse antibody against Na+/K+ ATPase was used as biotinylation control. Protein markers for molecular weights from 10 to 250 kDa (PageRulerTM Plus Prestained Protein Ladder, Thermo Scientific, Rockford, IL, USA) were used as size standards in protein electrophoresis (SDS-PAGE) and Western blotting. Expression of Nav1.5 was quantified using the ImageJ software (National Institute of Health, NIH) available at http://rsb.info. nih.gov/ij. Intensity values for each band were determined as the integrated density (sum of pixel values) within a fixed area. To account for differences of these values between WT and I890Tdue to loading, I890T intensity values were normalized with the ratio between WT and I890T Na+/K+ ATPases.In silico Studies of I890TThe software tools ESyPred3D 1.0 [18], Modeller 9.9 [19] and CPHmodels [20] were used to build a model of the pore module of DII of Nav1.5, based on the structure of the bacterial voltage-gated sodium channel (NavAb) ([11]). The model was constructed as a chimera of NavAb and Nav1.5 as follows: the sequence of S1 to S4, as well as the loop S4 5, was that of NavAb; the sequence of S5, loop S5 6, and 
S6 was that of DII of Nav1.5. No further constraints were defined.Figure 2. I890T markedly decreases peak INa. Voltage dependence of sodium currents measured from WT and I890T cells. Whole cell currents were elicited by depolarizing potentials as shown in the inset. (A) MedChemExpress CPI-455 Representative whole cell sodium current density traces recorded from WT and I890T cells. (B) Current-voltage (I ) relationship. INa amplitude was normalized to the cell capacitance to obtain current density (INa density) values. Experimental CPI-455 site points represent the peak-amplitude of current density at each given voltage, for WT (filled circles) and I890T (open circles). Values are expressed as mean 6 SE. doi:10.1371/journal.pone.0053220.gNovel Nav1.5 Pore Mutation I890T Causes BrSTable 1. Biophysical parameters of WT and I890T channels.INa at 220 mVpA/pF WT I890T 252.066.5 235.963.4*ActivationSteady-state InactivationSlow inactivationRecovery from inactivationn15V1/2 (mV)232.060.3 227.360.3**k26.960.3 26.760.n18V1/2 (mV)284.960.9 284.260.k24.960.4 24.960.n10t (ms)243.2639.9 224.2635.nt (ms)n115?4 3.960.1 5?9 4.260.Activation and steady-state inactivation parameters were calculated by data fitting to Boltzmann functions (se.A plasmid containing the green fluorescent protein (GFP) gene (a kind gift from Dr. Kirstine Call? University of Copenhagen, Copenhagen, Denmark) allowed the identification of transfected cells. All experiments were performed 48 hours after transfection.Novel Nav1.5 Pore Mutation I890T Causes BrSNovel Nav1.5 Pore Mutation I890T Causes BrSFigure 1. Clinical and genetic characterization of the proband and his family. (A) Family pedigree with corresponding ECGs. Open symbols indicate clinically normal subjects and filled symbols mark clinically affected individuals. Plus signs indicate 25033180 the carriers of the mutation I890T and minus signs, non-carriers. The arrow identifies the proband. Basal ECG of the proband and ECGs at the time of the ajmaline test of the family members are presented. (B) Detail of the electropherograms obtained after SCN5A sequence analysis. The arrow indicates the nucleotide position 2669 of SCN5A, where a double peak (T to C heterozygote change, c.2669 T.C) was identified in the proband’s DNA. doi:10.1371/journal.pone.0053220.gdetected with the SuperSignal West Femto Chemiluminiscent substrate (Pierce). A mouse antibody against Na+/K+ ATPase was used as biotinylation control. Protein markers for molecular weights from 10 to 250 kDa (PageRulerTM Plus Prestained Protein Ladder, Thermo Scientific, Rockford, IL, USA) were used as size standards in protein electrophoresis (SDS-PAGE) and Western blotting. Expression of Nav1.5 was quantified using the ImageJ software (National Institute of Health, NIH) available at http://rsb.info. nih.gov/ij. Intensity values for each band were determined as the integrated density (sum of pixel values) within a fixed area. To account for differences of these values between WT and I890Tdue to loading, I890T intensity values were normalized with the ratio between WT and I890T Na+/K+ ATPases.In silico Studies of I890TThe software tools ESyPred3D 1.0 [18], Modeller 9.9 [19] and CPHmodels [20] were used to build a model of the pore module of DII of Nav1.5, based on the structure of the bacterial voltage-gated sodium channel (NavAb) ([11]). The model was constructed as a chimera of NavAb and Nav1.5 as follows: the sequence of S1 to S4, as well as the loop S4 5, was that of NavAb; the sequence of S5, loop S5 6, and S6 was that of DII of Nav1.5. No further constraints were defined.Figure 2. I890T markedly decreases peak INa. Voltage dependence of sodium currents measured from WT and I890T cells. Whole cell currents were elicited by depolarizing potentials as shown in the inset. (A) Representative whole cell sodium current density traces recorded from WT and I890T cells. (B) Current-voltage (I ) relationship. INa amplitude was normalized to the cell capacitance to obtain current density (INa density) values. Experimental points represent the peak-amplitude of current density at each given voltage, for WT (filled circles) and I890T (open circles). Values are expressed as mean 6 SE. doi:10.1371/journal.pone.0053220.gNovel Nav1.5 Pore Mutation I890T Causes BrSTable 1. Biophysical parameters of WT and I890T channels.INa at 220 mVpA/pF WT I890T 252.066.5 235.963.4*ActivationSteady-state InactivationSlow inactivationRecovery from inactivationn15V1/2 (mV)232.060.3 227.360.3**k26.960.3 26.760.n18V1/2 (mV)284.960.9 284.260.k24.960.4 24.960.n10t (ms)243.2639.9 224.2635.nt (ms)n115?4 3.960.1 5?9 4.260.Activation and steady-state inactivation parameters were calculated by data fitting to Boltzmann functions (se.