RESUMEN
The demographical history of France remains largely understudied despite its central role toward understanding modern population structure across Western Europe. Here, by exploring publicly available Europe-wide genotype datasets together with the genomes of 3234 present-day and six newly sequenced medieval individuals from Northern France, we found extensive fine-scale population structure across Brittany and the downstream Loire basin and increased population differentiation between the northern and southern sides of the river Loire, associated with higher proportions of steppe vs. Neolithic-related ancestry. We also found increased allele sharing between individuals from Western Brittany and those associated with the Bell Beaker complex. Our results emphasise the need for investigating local populations to better understand the distribution of rare (putatively deleterious) variants across space and the importance of common genetic legacy in understanding the sharing of disease-related alleles between Brittany and people from western Britain and Ireland.
Asunto(s)
Genética de Población , Humanos , Francia , Genoma Humano/genética , Demografía , Variación Genética , Alelos , Genotipo , Historia Medieval , Europa (Continente)RESUMEN
BACKGROUND: The Brugada syndrome is an inherited cardiac arrhythmia associated with high risk of sudden death. Although 20% of patients with Brugada syndrome carry mutations in SCN5A, the molecular mechanisms underlying this condition are still largely unknown. METHODS AND RESULTS: We combined whole-exome sequencing and linkage analysis to identify the genetic variant likely causing Brugada syndrome in a pedigree for which SCN5A mutations had been excluded. This approach identified 6 genetic variants cosegregating with the Brugada electrocardiographic pattern within the pedigree. In silico gene prioritization pointed to 1 variant residing in KCNAB2, which encodes the voltage-gated K(+) channel ß2-subunit (Kvß2-R12Q). Kvß2 is widely expressed in the human heart and has been shown to interact with the fast transient outward K(+) channel subunit Kv4.3, increasing its current density. By targeted sequencing of the KCNAB2 gene in 167 unrelated patients with Brugada syndrome, we found 2 additional rare missense variants (L13F and V114I). We then investigated the physiological effects of the 3 KCNAB2 variants by using cellular electrophysiology and biochemistry. Patch-clamp experiments performed in COS-7 cells expressing both Kv4.3 and Kvß2 revealed a significant increase in the current density in presence of the R12Q and L13F Kvß2 mutants. Although biotinylation assays showed no differences in the expression of Kv4.3, the total and submembrane expression of Kvß2-R12Q were significantly increased in comparison with wild-type Kvß2. CONCLUSIONS: Altogether, our results indicate that Kvß2 dysfunction can contribute to the Brugada electrocardiographic pattern.
Asunto(s)
Síndrome de Brugada/genética , Mutación con Ganancia de Función/genética , Canales de Potasio con Entrada de Voltaje/genética , Electrocardiografía , Femenino , Predisposición Genética a la Enfermedad/genética , Genotipo , Humanos , Masculino , Canal de Sodio Activado por Voltaje NAV1.5/genética , Linaje , Polimorfismo de Nucleótido Simple/genética , Canales de Potasio de la Superfamilia Shaker , Canales de Potasio Shal/genética , Secuenciación del ExomaRESUMEN
The Brugada syndrome (BrS) is a rare heritable cardiac arrhythmia disorder associated with ventricular fibrillation and sudden cardiac death. Mutations in the SCN5A gene have been causally related to BrS in 20-30% of cases. Twenty other genes have been described as involved in BrS, but their overall contribution to disease prevalence is still unclear. This study aims to estimate the burden of rare coding variation in arrhythmia-susceptibility genes among a large group of patients with BrS. We have developed a custom kit to capture and sequence the coding regions of 45 previously reported arrhythmia-susceptibility genes and applied this kit to 167 index cases presenting with a Brugada pattern on the electrocardiogram as well as 167 individuals aged over 65-year old and showing no history of cardiac arrhythmia. By applying burden tests, a significant enrichment in rare coding variation (with a minor allele frequency below 0.1%) was observed only for SCN5A, with rare coding variants carried by 20.4% of cases with BrS versus 2.4% of control individuals (P = 1.4 × 10(-7)). No significant enrichment was observed for any other arrhythmia-susceptibility gene, including SCN10A and CACNA1C. These results indicate that, except for SCN5A, rare coding variation in previously reported arrhythmia-susceptibility genes do not contribute significantly to the occurrence of BrS in a population with European ancestry. Extreme caution should thus be taken when interpreting genetic variation in molecular diagnostic setting, since rare coding variants were observed in a similar extent among cases versus controls, for most previously reported BrS-susceptibility genes.