C9orf72 and amyotrophic lateral sclerosis: Hyper-excitability has been reported in fALS and sALS patients (van Zundert et al., 2012), and also in induced pluripotent stem cell-derived motoneurons (i-motoneurons) generated from ALS patients that harbor mutations in SOD1, C9orf72, and FUS/TLS (Wainger et al., 2014).