Multitrait analysis expands genetic risk factors in cardioembolic stroke

Background and Purpose: The genetic architecture of cardioembolic stroke (CES) is still poorly understood. Atrial fibrillation (AF) is the main cause of CES, with which it shares heritability. We aimed to discover novel loci associated with CES by performing a Multitrait Analysis of the GWAS (MTAG) with atrial fibrillation genetic data. Methods: For the MTAG analysis we used the MEGASTROKE cohort, which comprises European patients with CES and controls (n=362,661) and an AF cohort composed of 1,030,836 subjects. Regional genetic pleiotropy of the significant results was explored using an alternative Bayesian approach with GWAS-pairwise method. A replication was performed in an independent European cohort comprising 9,105 subjects using a Genome Wide Association Study (GWAS). Results: MTAG-CES analysis revealed 40 novel and significant loci (p-value<5x10-8) associated with CES, four of which had not previously been associated with AF. A significant replication was assessed for eight novel loci: CAV1, IGF1R, KIAA1755, NEURL1, PRRX1, SYNE2, TEX41 and WIPF1, showing a p-value<0.05 in the CES vs controls independent analysis. KIAA1755, a locus not previously described associated with AF. Interestingly, 51 AF risk loci were not associated with CES according to GWAS-pairwise analysis. Gene Ontology (GO) analysis revealed that these exclusive AF genes from the 51 loci participate in processes related mainly to cardiac development, whereas genes associated with AF and CES participate mainly in muscle contraction and the conduction of electrical impulses. Conclusions: We found eight new loci associated with CES. In addition, this study provides novel insights into the pathogenesis of CES, highlighting multiple candidate genes for future functional experiments.