PITX2C deficiency promotes arrhythmogenic remodelling via oxidative stress in atrial myocytes

Genetic variants upstream of the paired-like homeodomain transcription factor 2 (PITX2) are the strongest risk variants associated with atrial fibrillation. However, the mechanisms downstream of PITX2 are not completely understood. Here, we explore the role of PITX2 in oxidative metabolism and stress as a unifying mechanism of arrhythmogenesis. Transcriptomic analysis of Pitx2c-deficient neonatal rat atrial myocytes indicates oxidative phosphorylation as the top dysregulated pathway. Extracellular flux analysis reveals a functional decrease in oxidative metabolism in Pitx2c-deficient atrial cardiomyocytes which was accompanied by an accumulation of mitochondrial-specific ROS. We additionally assessed cardiomyocyte calcium cycling and observed an increased frequency of pro-arrhythmogenic mechanisms including altered calcium traces. Further, we identified a role of PITX2C in the sarcomere, as Pitx2c-deficient atrial cardiomyocytes display altered Titin localization. Notably, we observe that antioxidant treatment with N-acetylcysteine partially attenuates arrhythmogenic phenotypes including abnormal calcium cycling and Titin organization in Pitx2c-deficient atrial cardiomyocytes. Together, these data suggest that PITX2C deficiency is associated with atrial metabolism defects that ramifies cardiomyocyte dysfunction through oxidative stress.