Biomedical subjects

Julien Barc

Publications and source records attributed to Julien Barc.

3 recordsLinked to original sources

PubMed2026

Automated patch clamp data improve variant classification and penetrance stratification for SCN5A-Brugada syndrome.

BACKGROUND AND AIMS: Brugada Syndrome (BrS) is an inherited arrhythmia disorder that causes an elevated risk of sudden cardiac death. Approximately 20% of patients with BrS have rare variants in SCN5A, which encodes the cardiac sodium channel NaV1.5. Genetic workup of BrS is often complicated by SCN5A variants of uncertain significance (VUS) and/or incomplete penetrance. This study deployed an SCN5A-BrS functional assay at cohort scale to facilitate the implementation of genetic and precision medicine. METHODS: All 252 missense and in-frame insertion/deletion SCN5A variants from a previously published large cohort of BrS cases (n = 3335 patients) were analysed using a calibrated high-throughput automated patch-clamp (APC) assay. Variant functional Z-scores were assigned evidence levels ranging from BS3_moderate (normal function) to PS3_strong (loss-of-function), as defined by American College of Medical Genetics and Genomics criteria. Functional evidence was combined with population frequency, hotspot, case counts, protein-length changes, and in silico predictions. Odds ratios of BrS case-control enrichment and penetrance for BrS were calculated from variant frequencies in the BrS cohort and in gnomAD. RESULTS: Most variants (146/252) were functionally abnormal (Z ≤ -2), with 100 having severe loss-of-function (Z ≤ -4). Functional evidence enabled the reclassification of 110 of 225 VUS; 104 to likely pathogenic and 6 to likely benign. SCN5A variants with loss-of-function were mainly localized to the transmembrane domains, especially the regions comprising the central pore. SCN5A variant penetrance was proportional to the severity of loss-of-function; variants with Z ≤ -6 had penetrance of 24.5% (15.9%-37.7% CI) and an odds ratio of 501 for BrS. CONCLUSIONS: This cohort-scale APC dataset stratifies SCN5A variants found in BrS patients into normal function 'bystander' variants that have a low risk of BrS and loss-of-function variants that have a high risk for BrS. Functional data can be integrated with other criteria to reclassify a substantial fraction of VUS. The dataset helps clarify the SCN5A-BrS relationship and will improve the diagnosis and clinical management of BrS probands and their families.

Humans↗

PubMed2026

Whole-genome sequencing implicates rare, low-frequency and structural non-coding variation at the SCN5A locus in Brugada syndrome.

Brugada syndrome (BrS) is an inherited cardiac condition characterized by a hallmark ECG pattern and an increased risk of sudden cardiac death. Central to the aetiology of BrS, the SCN5A region harbours both common non-coding risk variants and rare coding variants that are causative in approximately 20% of patients. However, rare non-coding genetic variation in this region remains largely unexplored. Here, we used whole-genome sequencing (WGS) of 752 European-ancestry BrS cases and 1,827 ancestry-matched controls to identify BrS-associated rare non-coding genetic variation at the SCN5A locus. Sliding-window and cis-regulatory element (CRE)-based rare-variant aggregate testing implicated three conserved CREs, including a dense aggregation of case singleton variants within a 178 bp enhancer in intron 17 of SCN5A which replicated in an independent BrS cohort. Prioritised BrS-associated rare and low-frequency non-coding variants within these elements were predicted to alter cardiac transcription factor motifs, and altered CRE activity in hiPSC-CM luciferase assays or were associated with BrS-relevant ECG endophenotypes in the UK Biobank. Single-variant analysis across the region identified a Bonferroni-significant five-fold case-enriched low-frequency variant within a known CRE in intron 1 of SCN5A, which replicated, was associated with slower cardiac conduction in the UK Biobank and accounted for part of the BrS GWAS signal at this locus. Structural variant analyses identified a 10.5 kb deletion upstream of SCN5A in a BrS case that encompassed a cardiac CRE and reduced sodium current density in a hiPSC-CM model, as well as a 6 kb BrS-enriched retrotransposon insertion in SCN5A that appeared to underlie part of the GWAS signal in this region. Together, these findings implicate rare and low-frequency non-coding variation at the SCN5A locus in BrS susceptibility and demonstrate the value of targeted WGS analysis of key disease loci.

Journal Article↗

PubMed2024

Genome-Wide Association Study of Accessory Atrioventricular Pathways.

IMPORTANCE: Understanding of the genetics of accessory atrioventricular pathways (APs) and affiliated arrhythmias is limited. OBJECTIVE: To investigate the genetics of APs and affiliated arrhythmias. DESIGN, SETTING, AND PARTICIPANTS: This was a genome-wide association study (GWAS) of APs, defined by International Classification of Diseases (ICD) codes and/or confirmed by electrophysiology (EP) study. Genome-wide significant AP variants were tested for association with AP-affiliated arrhythmias: paroxysmal supraventricular tachycardia (PSVT), atrial fibrillation (AF), ventricular tachycardia, and cardiac arrest. AP variants were also tested in data on other heart diseases and measures of cardiac physiology. Individuals with APs and control individuals from Iceland (deCODE Genetics), Denmark (Copenhagen Hospital Biobank, Danish Blood Donor Study, and SupraGen/the Danish General Suburban Population Study [GESUS]), the US (Intermountain Healthcare), and the United Kingdom (UK Biobank) were included. Time of phenotype data collection ranged from January 1983 to December 2022. Data were analyzed from August 2022 to January 2024. EXPOSURES: Sequence variants. MAIN OUTCOMES AND MEASURES: Genome-wide significant association of sequence variants with APs. RESULTS: The GWAS included 2310 individuals with APs (median [IQR] age, 43 [28-57] years; 1252 [54.2%] male and 1058 [45.8%] female) and 1 206 977 control individuals (median [IQR] year of birth, 1955 [1945-1970]; 632 888 [52.4%] female and 574 089 [47.6%] male). Of the individuals with APs, 909 had been confirmed in EP study. Three common missense variants were associated with APs, in the genes CCDC141 (p.Arg935Trp: adjusted odds ratio [aOR], 1.37; 95% CI, 1.24-1.52, and p.Ala141Val: aOR, 1.55; 95% CI 1.34-1.80) and SCN10A (p.Ala1073Val: OR, 1.22; 95% CI, 1.15-1.30). The 3 variants associated with PSVT and the SCN10A variant associated with AF, supporting an effect on AP-affiliated arrhythmias. All 3 AP risk alleles were associated with higher heart rate and shorter PR interval, and have reported associations with chronotropic response. CONCLUSIONS AND RELEVANCE: Associations were found between sequence variants and APs that were also associated with risk of PSVT, and thus likely atrioventricular reentrant tachycardia, but had allele-specific associations with AF and conduction disorders. Genetic variation in the modulation of heart rate, chronotropic response, and atrial or atrioventricular node conduction velocity may play a role in the risk of AP-affiliated arrhythmias. Further research into CCDC141 could provide insights for antiarrhythmic therapeutic targeting in the presence of an AP.

Humans↗