STXBP1 and atrial fibrillation: Expression of SCN8A, NALCN, SATB2, TCF4 and STXBP1 was detected in fibroblasts, whereas expression of SCN8A, NALCN, KIF1A, PAK3, SATB2, TCF4, and STXBP1 was detected in AF cells (Fig. 2d).