👤 Bernd Kirchhof

Hypertrophic cardiomyopathy (HCM) is an inherited cardiomyopathy often caused by pathogenic variants in MYBPC3 and MYH7, encoding myosin-binding protein C3 and myosin heavy chain 7, respectively. These variants can cause increased actin-myosin crossbridge cycling, resulting in ventricular hypercontractility, but mice lacking Mybpc3 exhibited reduced left ventricular ejection time (LVET) as a sign of systolic dysfunction. In this study, we tested whether LVET is specifically altered in patients carrying MYBPC3 variants by retrospective echocardiographic analysis in two genotype-defined HCM cohorts. LVET was measured by echocardiography and adjusted for heart rate [LVET index (LVETI)] in 166 patients. Variant carriers were stratified for the presence (LVH+) or absence of left ventricular hypertrophy with septal thickness of ≥13 mm (LVH-). Multivariate analysis of variance (MANOVA) was used to identify differences in LVETI between variant carriers and controls with LVETI as the dependent variable, adjusted for sex, age, left ventricular ejection fraction (LVEF), interventricular septal diameter in diastole (IVSd), diastolic dysfunction, left ventricular outflow tract (LVOT) gradient at rest and medication history as confounders. In a total of 166 patients carrying MYBPC3 or MYH7 pathogenic variants (38 ± 3 years, 45% female), we compared the discovery cohort (40 MYBPC3 and 31 MYH7) and the validation cohort ('Valsartan in Attenuating Disease Evolution in Early Sarcomeric HCM'; 54 MYBPC3 and 41 MYH7) with 44 healthy controls. LVETI was lower in MYBPC3 and higher in MYH7 LVH+ patients than in controls in the discovery, validation and pooled cohorts (pooled: MYBPC3 381 ± 19 ms vs. MYH7 437 ± 38 ms, P < 0.001; MYBPC3 vs. controls 411 ± 15 ms, P < 0.001; and MYH7 vs. controls, P < 0.001). Similar findings were seen in LVH- (pooled: MYBPC3 380 ± 16 ms vs. MYH7 437 ± 39 ms, P < 0.001; MYBPC3 vs. controls, P < 0.001). While MYH7 variants were all missense as expected, 87% of the MYBPC3 variants were truncating (including nonsense variants, out-of-frame deletion and splice site variants) and 13% were non-truncating (missense and in-frame deletion). LVETI did not differ between the groups and was significantly lower than the control in both. The data suggest that variants in MYBPC3 and MYH7 result in distinct biophysical consequences, which can be detected by measuring LVETI in patients. The findings may have implications for potential genotype-specific differences in response to therapies targeting sarcomere function. Show less

Atrial fibrillation (AF) is a prevalent and morbid abnormality of the heart rhythm with a strong genetic component. Here, we meta-analyzed genome and exome sequencing data from 36 studies that included 52,416 AF cases and 277,762 controls. In burden tests of rare coding variation, we identified novel associations between AF and the genes MYBPC3, LMNA, PKP2, FAM189A2 and KDM5B. We further identified associations between AF and rare structural variants owing to deletions in CTNNA3 and duplications of GATA4. We broadly replicated our findings in independent samples from MyCode, deCODE and UK Biobank. Finally, we found that CRISPR knockout of KDM5B in stem-cell-derived atrial cardiomyocytes led to a shortening of the action potential duration and widespread transcriptomic dysregulation of genes relevant to atrial homeostasis and conduction. Our results highlight the contribution of rare coding and structural variants to AF, including genetic links between AF and cardiomyopathies, and expand our understanding of the rare variant architecture for this common arrhythmia. Show less

To analyze the association between polymorphisms in the TIMP3 gene and genes of the high-density lipoprotein (HDL) metabolism and age-related macular degeneration (AMD), and evaluate serum lipid and lipoprotein levels in AMD patients compared with control individuals. Single nucleotide polymorphisms in or near the TIMP3, ABCA1, FADS1-3, CETP, LIPC, and LPL genes were genotyped. Serum levels of apolipoprotein B (ApoB), apolipoprotein A1, lipoprotein a, cholesterol, triglycerides, and HDL-cholesterol were determined. Significant associations were found between AMD and variants in ABCA1 and FADS1-3, and a nearly significant association in TIMP3. No significant associations were observed for variants in LPL, LIPC, and CETP. We also observed a significant elevation of ApoB levels in serum of AMD patients. Other lipids and lipoproteins were not significantly altered. These results confirm associations of AMD with variants near the TIMP3 gene and at loci involved in HDL metabolism. They further highlight a role of the extracellular matrix and the HDL metabolism in the pathogenesis of AMD. This study identified increased ApoB levels as a possible new serum biomarker for AMD. Show less