Abstract Introduction Dilated cardiomyopathy (DCM) is a primary heart muscle disease characterized by ventricular dilatation and impaired contractility. While considered a Mendelian disorder, recent evidence highlights the important role of common genetic variation. Better characterization of the genetic architecture will provide opportunities for improved diagnosis, risk stratification and biological understanding. Methods We performed a GWAS meta-analysis of 14,256 DCM cases and 1,185,671 controls of European ancestry from 16 studies (GWASDCM). To improve discovery power, we performed multi-trait analysis of GWAS (GWASMTAG) with three genetically correlated and clinically relevant cardiac imaging traits in 36,203 individuals. To identify effector genes at loci, we used a two-step approach: 1) the nearest gene and top 3 genes prioritized by PoPS or V2G were selected as candidates; and 2) totality of evidence including 5 additional methods (coding variant, co-localization with expression, TWAS, ABC-model, and known Mendelian cardiomyopathy genes) was summarized in a single score. We performed rare variant burden analysis (MAF<0.1%) for predicted truncating variants (PTV) in established DCM-causing genes to highlight DCM genetic architecture, and in prioritized GWAS genes, against DCM and quantitative CMR traits in UK Biobank (UKB) and 100,000 Genomes Project (GeL), implemented by REGENIE. A polygenic score (PGS) generated using a Bayesian framework (PRS-CS) was assessed for association with the same outcomes in UKB participants, including among PTV carriers in established DCM-causing genes. Results We identified 80 independent loci, of which 65 were novel (62 loci in GWASDCM, and 54 loci in GWASMTAG) (Figure 1A). High-confidence genes were prioritized at 62 loci, including in genes with established roles in Mendelian cardiomyopathies (TTN, BAG3, FLNC, MYBPC3, FHOD3, ALPK3), and were enriched in key biological processes (Figure 1B). We characterized DCM genetic architecture across the allelic spectrum (Figure 2A). Rare variant burden analysis highlighted novel associations with DCM and quantitative traits for PTVs in NEDD4L and MAP3K7 in UKB that were replicated in GeL (Figure 2B). PGS was associated with DCM and quantitative CMR traits (OR per PGS SD 1.8, P<1x10-16) (Figure 2C). Individuals in the top centile had 4-fold increased risk of having DCM compared with median risk. PGS stratified penetrance of rare variants in 1,546 carriers of pathogenic variants (top quintile 7.3%, bottom quintile 1.7%, P 0.005). Conclusion We have performed the largest DCM GWAS, resulting in 80 significant loci (65 novel), and prioritized genes using a systematic approach. We identify novel DCM-causing genes (NEDD4L and MAP3K7) and generate a PGS that associates with DCM and modulates penetrance in carriers of Mendelian disease-causing rare variants.Figure 1Figure 2
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