Dysregulation of N-terminal acetylation causes cardiac arrhythmia and cardiomyopathy

BACKGROUNDN-terminal-acetyltransferases catalyze N-terminal acetylation (Nt-acetylation), an evolutionarily conserved co-translational modification. Nt-acetylation regulates diverse signaling pathways, yet little is known about its effects in the heart. To gain insights, we studied NAA10-related syndrome, in which mutations in NAA10, which catalyzes Nt-acetylation, causes severe QT prolongation, hypotonia, and neurodevelopmental delay. METHODSWe identified a missense variant in NAA10 (c.10C>A; p.R4S) that segregated with severe QT prolongation, arrhythmia, cardiomyopathy, and sudden death in a large kindred. We developed patient-derived and genome-edited human induced pluripotent stem cell (iPSC) models and deeply phenotyped iPSC-derived cardiomyocytes (iPSC-CMs) to dissect the mechanisms underlying NAA10-mediated cardiomyocyte dysfunction. RESULTSThe NAA10-R4S mutation reduced enzymatic activity, decreased expression levels of NAA10/NAA15 proteins, and destabilized the NatA complex. In iPSC-CM models of NAA10 dysfunction, dysregulation of the late sodium and slow rectifying potassium currents caused severe repolarization abnormalities, consistent with clinical QT prolongation and increased risk for arrhythmogenesis. Engineered heart tissues generated from mutant NAA10 cell lines had significantly decreased contractile force and sarcomeric disorganization, consistent with the cardiomyopathic phenotype in the identified family members. Diastolic calcium levels were increased with corresponding alterations in calcium handling pathways. We identified small molecule and genetic therapies that reversed the effects of NAA10 dysregulation of iPSC-CMs. CONCLUSIONSOur study defines novel roles of Nt-acetylation in cardiac ion channel regulation and delineates mechanisms underlying QT prolongation, arrhythmia, and cardiomyopathy caused by NAA10 dysfunction.