Even in the presence of cortical neurons, the majority of CX43 expression was observed at the boundary between AF cells and GFAP-positive astrocytes (Figures 5(a)-5(b)), arrowheads); whereas a negligible amount of Cx43 protein was observed between AF cells and neurons at the interface of neurites and the AF cell membrane (Figures 5(a)-5(b)), arrows). This evidence concerns the gene GJA1 and atrial fibrillation.