In addition, the expression of gap junction (GJ) proteins, such as connexin 43 (Cx43), is relatively low in iPSC-CMs, and the electrical conduction is uneven as the heart rhythm increases [16,25], this electrical heterogeneity is also one of the main causes of arrhythmia after transplantation [16,24]. The gene discussed is GJA1; the disease is cardiac arrhythmia.