Identification of Gender-specific Genetic Variants Associated with Bicuspid Aortic Valve

Natasha Dargis^a, Maxime Lamontagne^a, Nathalie Gaudreault^a, Laura Sbarra^a, Cyndi Henry^a, Philippe Pibarot^a, Patrick Mathieu^a, Yohan Bossé^ab

a. Centre de recherche de l’Institut universitaire de cardiologie et de pneumologie de Québec (CRIUCPQ), Quebec City, QC, Canada; b. Department of Molecular Medicine, Laval University, Quebec City, QC, Canada

Background. Bicuspid aortic valve (BAV) is the most frequent congenital heart defect and has a male predominance of 3 to 1. The majority of patients with BAV develop serious valvular and aortic complications. Despite the high prevalence of BAV, its etiology and genetic origins remain elusive. The goal of this study was to improve our understanding of the genetic components involved in the development of BAV.

Methods. The coding sequence, UTRs and promoter of nine candidate genes for BAV (NOTCH1, AXIN1, EGFR, ENG, GATA5, NKX2-5, NOS3, PDIA2 and TGFBR2) were sequenced in 48 BAV patients using the Ion Torrent PGM system. Pathogenicity of variants was evaluated with the Combined Annotation Dependant Depletion (CADD) framework. A selection of 96 variants identified in our BAV patients and previously published BAV-associated variants across the genome were genotyped using the Illumina BeadXpress system. Allele frequencies were compared in 339 patients with BAV confirmed at surgery and 606 controls. Analyses were also performed by gender.

Results. Sixteen novel and 19 potentially pathogenic variants were identified by next-generation sequencing and subsequently confirmed by Sanger sequencing, but they were not associated with BAV in our case-control population. However, a significant association was observed between an in silico-predicted benign EGFR intronic variant (rs17290301) and BAV. Analyses performed by gender revealed different variants associated with BAV in males (EGFR Y2626Y and TEX26 rs12857479) and females (NOTCH1 rs61751489, TGFBR2 rs1155705 and NKX2-5 rs2277923).

Conclusions. We identified novel and previously known potentially pathogenic genetic variants in nine candidate genes for BAV. None were associated with BAV in our case-control population, which is likely to be explained by their low frequencies. Other variants were associated with BAV, particularly in stratified analyses by gender, supporting a possible role of gender-specific polymorphisms in the development of BAV. Further analyses are required to evaluate the functional impacts of these variants.