GPD1L-A306del modifies sodium current in a family carrying the dysfunctional SCN5A-G1661R mutation associated with Brugada syndrome

Figures

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  Fig. 1. Affected members and ECG abnormalities in the BrS family. (A) Pedigree of the family. Filled symbols indicate BrS affected individuals, pointed symbols denote gene carrying individuals and open symbols unaffected family members. The genotype of each individual, if known, is reported on the bottom: + / + indicates WT, ± heterozygous and -/- homozygous genotype. (B) Ventricular fibrillation episode with ICD shock in individual II.3. (C) Spontaneous type I BrS ECG of individual II.3. (D) Spontaneous type I BrS ECG of individual II.2

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  Fig. 2. Both identified variants are localized in highly conserved regions of the respective proteins. (A) Scheme of the sodium channel and sequence of the subregion 5 of domain IV. The localization of the reported variant is symbolized with an orange triangle. (B—C) Alignment of parts of the SCN5A and GPD1L proteins from various species. The variants, written in orange, are located in highly conserved regions among the species

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  Fig. 3. SCN5A-G1661R produces non-functional channels. (A) Representative current traces of cells transfected exclusively with the WT, the mutant or equivalent amounts of both SCN5A plasmids. (B) Current voltage relationship for WT (black circles) and SCN5A heterozygous (grey circles) transfected cells. The solid lines were determined using Eq. (1) with the averaged parameters. (C) Mean current density for each type of cell determined by normalizing the mean current at -10 mV to the mean cell capacitance. The mean cell capacitances were 11.5 ± 0.7 pF (SCN5A-WT), 13.1 ± 0.9 pF (SCN5A-WT + SCN5A-G1661R) and 11.9 ± 0.8 pF (SCN5A-G1661R), resp. *p < 0.05, ****p < 0.0001 vs SCN5A-WT

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  Fig. 4. GPD1L changes the steady-state activation and inactivation properties of the sodium channels. (A) Current voltage relationship for cells transfected either exclusively with the WT SCN5A plasmid (black circles) or co-expressed with the WT GPD1L plasmid (black squares). The solid lines were determined using Eq. (1) with the averaged parameters. (B) Mean current density for each type of cell determined by normalizing the mean current at -10 mV to the mean cell capacitance. The mean cell capacitances were 11.5 ± 0.7 pF (SCN5A-WT) and 11.3 ± 0.7 pF (SCN5A-WT + GPD1L-WT), resp. (C-D) Voltage dependence of steady-state activation (C) and inactivation (D). The solid lines were determined using Eqs. (1) and (2) with the averaged parameters

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  Fig. 5. GPD1L-A306del shifts the steady-state activation of the sodium channels towards hyperpolarization, while altering the steady-state inactivation toward depolarization. (A) Current voltage relationship for cells transfected with the WT SCN5A plasmid co-expressed either with the GPD1L WT (black squares), mutant (white squares) or both plasmids (grey squares). The solid lines were determined using Eq. (1) with the averaged parameters. (B) Mean current density for each type of cell determined by normalizing the mean current at -10 mV to the mean cell capacitance. The mean cell capacitances were 11.3 ± 0.7 pF (SCN5A-WT + GPD1L-WT), 12.7 ± 0.6 pF (SCN5A-WT + GPD1L-WT + GPD1L-A306del) and 13.1 ± 0.5 pF (SCN5A-WT + GPD1L-A306del), resp. (C-D) Voltage dependence of steady-state activation (C) and inactivation (D). The solid lines were determined using Eqs. (1) and (2) with the averaged parameters

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  Fig. 6. SCN5A-G1661R and GPD1L-A306del co-expression changes the steady-state activation and inactivation properties of the sodium channels, while reducing the sodium current. (A) Current voltage relationship for cells transfected with the WT and mutant SCN5A plasmid co-expressed either with the WT (black triangles), the mutant (white triangles) or both GPD1L plasmids (grey triangles). The solid lines were determined using Eq. (1) with the averaged parameters. (B) Mean current density for each type of cell determined by normalizing the mean current at -10 mV to the mean cell capacitance. The mean cell capacitances were 11.3 ± 0.7 pF (SCN5A-WT + GPD1L-WT), 12.8 ± 0.6 pF (SCN5A-WT + SCN5A-G1661R + GPD1L-WT), 14.7 ± 1.1 pF (SCN5A-WT + SCN5A-G1661R + GPD1L-WT + GPD1L-A306del) and 16.2 ± 1.2 pF (SCN5A-WT + SCN5A-G1661R + GPD1L-A306del), resp. (C-D) Voltage dependence of steady-state activation (C) and inactivation (D). The solid lines were determined using Eqs. (1) and (2) with the averaged parameters. *p < 0.05 vs SCN5A-WT + GPD1L-WT