BAG3 and familial dilated cardiomyopathy: Emphasizing the role of gene dosage as a likely mechanism of action at GWAS genes28 and the continuum of disease risk, four of the seven definitive evidence Mendelian DCM genes, established to act through mechanisms involving reduced gene product29, were identified through GWAS: TTN, FLNC, LMNA and BAG3. We observed a tenfold enrichment of Mendelian cardiomyopathy genes within GWAS loci (odds ratio (OR) = 9.7, P = 1.1 × 10−6).