Human mutations in the gene encoding Cx40, GJA5, have been reported to cause atrial fibrillation [15], and the deletion of Cx40 in murine models results in myocardial hypertrophy, fibrosis, arrhythmia, and conduction disturbances (i.e. increased P-wave and QRS duration) [16]. The gene discussed is GJA5; the disease is cardiac arrhythmia.