SCN5A and atrial fibrillation: Nevertheless, the potential importance of β-subunits in SCN5A modulation has been suggested by arrhythmia-associated mutations in all four β-subunit genes, including mutations causing Brugada syndrome (Watanabe et al., 2008; Hu et al., 2009; Hu et al., 2012), LQT3 (Medeiros-Domingo et al., 2007; Riuro et al., 2014), and atrial fibrillation (Watanabe et al., 2009; Olesen et al., 2011).