Abstract P1037: Dysfunction Of N-terminal Acetylation Causes Multiple Electrical Abnormalities Leading To Long QT Syndrome And Dilated Cardiomyopathy

Abstract

Introduction: NAA10-related syndrome is characterized by long QT syndrome (LQTS), cardiomyopathy, hypotonia, and neurodevelopmental delay. NAA10 complexes with the regulatory subunit NAA15 to make the post-translationally modifying N-terminal acetyltransferase, NatA. Despite the association of LQTS and NAA10 mutations, the mechanism is unknown. Hypothesis: NAA10 dysfunction affects the function of cardiac ion channels or related proteins causing LQTS, and sarcomere abnormalities causing cardiomyopathy. Methods: Target sequencing of large kindred with multiple family members who had LQTS and sudden death revealed a segregating mutation in NAA10 (c.10C>A; p.R4S). Somatic cell reprogramming was used to create an induced pluripotent stem cell (iPSC) line from a gene-positive male patient with LQTS and dilated cardiomyopathy (pNAA10 R4S ). Genome-editing was used to create the control iPSC line (eNAA10 R4S ). iPSC lines were differentiated into cardiomyocytes (iPSC-CMs) for further analysis. In addition, we performed biochemical assays to investigate the enzymatic activities of the NAA10-R4S mutation. Results: The NAA10-R4S mutation had reduced enzymatic activity, decreased expression levels of NAA10/NAA15 and destabilized the NatA complex. Action potential duration was prolonged in pNAA10 R4S - and eNAA10 R4S -iPSC-CMs as compared to WT iPSC-CMs (498.9 ± 38.8 ms and 514.1 ± 52.9 ms, vs 316.7 ± 48.2 ms; p<0.05). Investigation of the underlying ion channel currents revealed increased late I Na (Late I Na / Peak I Na : pNAA10 R4S : 0.062 ± 0.010 % and eNAA10 R4S : 0.074 ± 0.020 % vs. WT: 0.026 ± 0.005 %; p<0.05) and reduced I Ks (pNAA10 R4S : 0.18 ± 0.05 pA/pF and eNAA10 R4S : 0.26 ± 0.04 pA/pF vs. WT: 0.61 ± 0.15 pA/pF; p<0.05). There were no significant differences in I Kr and I CaL . Diastolic Ca 2+ levels were increased in mutant iPSC-CMs (F340/F380: 0.18 ± 0.02 vs 0.04 ± 0.01; p<0.05) consistent with impaired Ca 2+ handling. Plating iPSC-CMs on micro-contact printed islands revealed alterations in sarcomeric structure. Conclusion: We demonstrate that the NAA10 mutation cause abnormalities in ion channels and sarcomere development. Our data indicated a novel role for N-terminal acetylation in cardiac ion channel regulation leading to cardiovascular disorders.