Homozygous Cx43(K258stop) mice are not viable due to severe edema, attributed to loss of the epithelial junctional barrier10; mice heterozygous for truncated Cx43 (Cx43K258/−) show defective migration of neuronal precursors11, altered intercalated disc structure and localization12 and predisposition to cardiac arrhythmias and larger infarct size after cardiac or cerebral ischemia13,14. Here, GJA1 is linked to cardiac arrhythmia.