Pathogenic variants in myoferlin (MYOF) cause arrhythmogenic cardiomyopathy

Arrhythmogenic cardiomyopathy (ACM) is an inherited disease characterized by fibrofatty remodeling and sudden cardiac death linked to desmosomal dysfunction. Yet, 40% of cases remain genetically unexplained, and non-desmosomal mutations offer insight into ACM pathophysiology. Myoferlin (MYOF), a calcium (Ca2+)-binding protein in cardiomyocytes, is linked to cardiomyopathy, but its mechanism remains unknown. Whole-exome sequencing identified a heterozygous MYOF missense variant (p.G1654S) in an ACM family; we subsequently found three unrelated p.G1654S cases. We hypothesized that MYOF deficiency promotes Ca2+ handling deficits and arrhythmogenesis in ACM. In patient iPSC-derived cardiomyocytes, MYOF p.G1654S protein dimerized with wild-type protein and underwent accelerated lysosomal degradation, showed disrupted Ca2+ handling, and displayed increased arrhythmia burden, all rescued by genomic correction. MYOF interacted with CaV1.2, and verapamil pharmacologically rescued arrhythmias. Heterozygous Myof knockout mice showed systolic dysfunction and fibrosis. These findings establish MYOF as a causative ACM gene and therapeutic target that mediates arrhythmogenesis by disrupting MYOF-CaV1.2.