We therefore measured the spontaneous mutation rate in four induced pluripotent stem cell (iPSC) lines generated from two familial ALS patients harboring a heterozygous TDP-43(M337V) or TDP-43(Q343R) mutation (Egawa et al., 2012), and in three control iPSC lines (Zhang et al., 2013). The gene discussed is TARDBP; the disease is amyotrophic lateral sclerosis.