SCN1A and Dravet syndrome: For example, gain of function mutations of both the Nav1.2 (Kearney et al., 2001; Misra et al., 2008; Ogiwara et al., 2009; Liao et al., 2010) and Nav1.6 (O’Brien and Meisler, 2013; Gardella and Moller, 2019; Johannesen et al., 2019) have been demonstrated to cause severe epilepsies, while loss of function mutations of Nav1.1 is the main cause of Dravet syndrome (Catterall et al., 2010; Bender et al., 2012; Cheah et al., 2012; Catterall, 2018).