To date, studies have reported reduced HCN1 expression in AD patients (Saito et al., 2012) as well as mutation or loss of VAPB, an HCN regulator protein in ALS (Anagnostou et al., 2010; Mitneneto et al., 2011) and SMA patients (Nishimura et al., 2004). Here, VAPB is linked to proximal spinal muscular atrophy.