GJA5 and atrial fibrillation: Of note, our study did not show any association of AF (either structural or non-structural) with the promoter A polymorphisms, Cx40 − 44/+71; these polymorphisms were also shown to reduce GJA5 expression in vitro by about 50%; however, Wirka et al. showed no effect on GJA5 expression in atrial tissue, suggesting that promoter A is not necessary to Cx40 expression in atrial myocytes [34].