ABSTRACT
AIMS: The aim of this study was to determine the frequency of heterozygous truncating ALPK3 variants (ALPK3tv) in patients with hypertrophic cardiomyopathy (HCM) and confirm their pathogenicity using burden testing in independent cohorts and family co-segregation studies. METHODS AND RESULTS: In a discovery cohort of 770 index patients with HCM, 12 (1.56%) were heterozygous for ALPK3tv [odds ratio(OR) 16.11, 95% confidence interval (CI) 7.94-30.02, P = 8.05e-11] compared to the Genome Aggregation Database (gnomAD) population. In a validation cohort of 2047 HCM probands, 32 (1.56%) carried heterozygous ALPK3tv (OR 16.17, 95% CI 10.31-24.87, P < 2.2e-16, compared to gnomAD). Combined logarithm of odds score in seven families with ALPK3tv was 2.99. In comparison with a cohort of genotyped patients with HCM (n = 1679) with and without pathogenic sarcomere gene variants (SP+ and SP-), ALPK3tv carriers had a higher prevalence of apical/concentric patterns of hypertrophy (60%, P < 0.001) and of a short PR interval (10%, P = 0.009). Age at diagnosis and maximum left ventricular wall thickness were similar to SP- and left ventricular systolic impairment (6%) and non-sustained ventricular tachycardia (31%) at baseline similar to SP+. After 5.3 ± 5.7 years, 4 (9%) patients with ALPK3tv died of heart failure or had cardiac transplantation (log-rank P = 0.012 vs. SP- and P = 0.425 vs. SP+). Imaging and histopathology showed extensive myocardial fibrosis and myocyte vacuolation. CONCLUSIONS: Heterozygous ALPK3tv are pathogenic and segregate with a characteristic HCM phenotype.
Subject(s)
Cardiomyopathy, Hypertrophic , Muscle Proteins/genetics , Protein Kinases/genetics , Cardiomyopathy, Hypertrophic/genetics , Heterozygote , Humans , Mutation , SarcomeresABSTRACT
TMEM43 (LUMA) is a ubiquitously expressed protein with unknown function. The protein is phylogenetically highly conserved and also found in Drosophila melanogaster (Klinke et al., 2022). TMEM43-p.S358L is a rare, fully penetrant mutation that leads to arrhythmogenic right ventricular cardiomyopathy type 5 (ARVC5). To understand the function of the ARVC5-associated mutation it is first important to understand the function of the TMEM43 protein. Therefore, a TMEM43 knockout induced pluripotent stem cell (iPSC) line was generated using the CRISPR/Cas9 genome editing system. The resulting cell line had a deficiency of TMEM43 and showed normal morphology and a stable karyotype. The colonies were positive for pluripotency markers and could be differentiated into the three germ layers.