Abstract 16184: Modeling a NPPA Mutation Linked With Atrial Fibrillation Using Atrial Human Induced Pluripotent Stem Cell Derived Cardiomyocytes.

Background: We identified the first non-ion channel gene (NPPA) encoding atrial natriuretic peptide (ANP) linked with familial atrial fibrillation (AF). However, the underlying mechanisms by which NPPA mutations cause AF remain unclear. Objective: To elucidate the underlying molecular and electrophysiologic mechanisms of a novel AF-linked NPPA mutation using patient specific atrial human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). Methods: Blood was collected from an AF proband carrying a novel NPPA- S64R mutation with early-onset AF and an unaffected family member not harboring the variant (Fig. 1A). Patient-specific hiPSCs were generated from peripheral blood mononuclear cells. Atrial CMs were generated through a novel retinoic acid (RA) enriching protocol. Results: RA-guided differentiation of hiPSC-CMs generated atrial action potential (AP) morphologies in ≥85% of cells validating our atrial hiPSC-CM model (Fig. 1B). RNA-seq and qPCR demonstrated significant downregulation of Na+ channels including β-subunits in mutant vs control atrial hiPSC-CMs (Fig. 1C-D) and KCNE1 but no change in expression of KCNQ1 and CACNA2D1. Single cell patch clamping revealed a shortened APD in NPPA mutant atrial CMs and a reduced peak Na+ current (INa; Fig. 1E) and density creating a reentrant substrate for AF. Conclusion: Using atrial hiPSC-CMs, we showed that an NPPA AF-linked mutation modulates multiple cardiac ion channels leading to APD shortening creating a reentrant substrate for AF. Thus, modeling AF-linked mutations using atrial hiPSC-CMs may offer a novel platform for identifying novel therapeutic targets for family members with AF. [ABSTRACT FROM AUTHOR]