GJA1 and atrioventricular block: Up-regulation of miR-1 in MI mice might be involved in the development of life-threatening arrhythmias such as ventricular tachycardia (VT), ventricular fibrillation, and atrioventricular block (AVB) by targeting the mRNAs of ion channel genes, i.e., KCNJ2 and GJA1 [16, 17], respectively.