Dysregulation of N-terminal acetylation causes cardiac arrhythmia and cardiomyopathy.

N-terminal acetyltransferases including NAA10 catalyze N-terminal acetylation, an evolutionarily conserved co- and post-translational modification. However, little is known about the role of N-terminal acetylation in cardiac homeostasis. To gain insight into cardiac-dependent NAA10 function, we studied a previously unidentified NAA10 variant p.(Arg4Ser) segregating with QT-prolongation, cardiomyopathy, and developmental delay in a large kindred. Here, we show that the NAA10(R4S) variant reduced enzymatic activity, decreased NAA10-NAA15 complex formation, and destabilized the enzymatic complex N-terminal acetyltransferase A. In NAA10(R4S/Y)-induced pluripotent stem-cell-derived cardiomyocytes (iPSC-CMs), dysregulation of the late sodium and slow delayed rectifier potassium currents caused severe repolarization abnormalities, consistent with clinical QT prolongation. Engineered heart tissues generated from NAA10(R4S/Y)-iPSC-CMs had significantly decreased contractile force and sarcomeric disorganization, consistent with the pedigree's cardiomyopathic phenotype. Proteomic studies revealed dysregulation of metabolic pathways and cardiac structural proteins. We identified small molecule and genetic therapies that normalized the phenotype of NAA10(R4S/Y)-iPSC-CMs. Our study defines the roles of N-terminal acetylation in cardiac regulation and delineates mechanisms underlying QT prolongation, arrhythmia, and cardiomyopathy caused by NAA10 dysfunction.