Novel SCN5A and GPD1L Variants Identified in Two Unrelated Han-Chinese Patients With Clinically Suspected Brugada Syndrome

Figures

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  Figure 1. Spontaneous electrocardiogram (ECG) of two patients. (A) ECG of Patient 1: Type 1 Brugada pattern displaying a coved-type ST-segment (≥2 mm) and negative T wave in V1 and V2, a first-degree atrioventricular block pattern, and an incomplete right bundle branch block. (B) ECG of Patient 2: Type 3 Brugada pattern displaying a saddleback ST-segment (<1 mm) in V2, and a first-degree atrioventricular block pattern.

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  Figure 2. Identified variants of the sodium voltage-gated channel alpha subunit 5 gene (SCN5A) and the glycerol-3-phosphate dehydrogenase 1 like gene (GPD1L) in the two patients. (A) Heterozygous transversion (c.2437-2A>C) at the splice acceptor site of SCN5A intron 15 in Patient 1. (B) The normal SCN5A sequence of an unaffected individual. (C) The GPD1L sequence with heterozygous c.161A>T [p.(Asp54Val)] variant in Patient 2. (D) The normal GPD1L sequence of an unaffected individual.

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  Figure 3. The conserved analysis and structural prediction of wildtype and mutant glycerol-3-phosphate dehydrogenase 1 like (GPD1L) proteins. (A) The GPD1L p.Asp54 amino acid residue is conserved in nine species by a multiple sequence alignment program. (B) Structural prediction of wildtype and variant GPD1L proteins.

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  Figure 4. Minigene assay for the sodium voltage-gated channel alpha subunit 5 gene (SCN5A) c.2437-2A>C variant and the schematic splicing model. (A) Electrophoresis of reverse transcription PCR products, with mRNA extracted from cells transfected with pMini-CopGFP-SCN5A (WT for wildtype: 1,063 bp, MT for mutant: 1,048/922 bp). (B) Sanger sequencing of the wildtype (1,063 bp) shows a junction between exons 15 and 16. (C) Sanger sequencing of the mutant (1,048 bp) indicates a deletion of 15 bp from exon 16. (D) Sanger sequencing of the mutant (922 bp) indicates a deletion of 141 bp from exon 16. (E) A schematic splicing mechanism of the SCN5A c.2437-2A>C variant. The continuous lines between exons show the normal splicing of the wildtype, and the dotted lines demonstrate the aberrant splicing, resulting in activation of two cryptic sites and partial loss of exon 16.

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  Figure 5. Variant frequency of genes related to Brugada syndrome (BrS). Each disease-causing or susceptibility gene corresponds to the year when it was first discovered to be related to BrS. The number in the circle indicates the percentage of variant frequency. The gene symbol used is approved by the HUGO Gene Nomenclature Committee.

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  Figure 6. Schematic representations of the sodium voltage-gated channel alpha subunit 5 gene (SCN5A) and the glycerol-3-phosphate dehydrogenase 1 like gene (GPD1L) and the encoded proteins, as well as the identified variants. Variants identified in this study are indicated by red colors. (A) The Brugada syndrome-1-related single nucleotide substitutions affecting splicing are shown in the SCN5A gene. SCN5A consists of four putative transmembrane domains (DI-DIV), with six transmembrane segments (S1–S6) for each section. The light purple-colored region on SCN5A is the segment encoded by the first 15 nucleotides of exon 16, and the dark red is encoded by the 16–141 nucleotides of exon 16. (B) The GPD1L gene variants related to Brugada syndrome-2 and sudden infant death syndrome are shown. GPD1L contains the glycerol-3-phosphate dehydrogenase (GPD) motif [nicotinamide adenine dinucleotide (phosphate)-binding domain, NAD(P)-bd] and 6-phosphogluconate dehydrogenase C-terminal domain-like (6-PGluconate_DH).