In these experiments, we chose ALS2-mutated iPSCs as a source because the mutation of ALS2 that we used results in UMN-dominant symptoms (Shirakawa et al., 2009) and ALS2 is also known to be a causative gene for other UMN diseases, such as primary lateral sclerosis (PLS) and hereditary spastic paraplegia (HSP; Chandran et al., 2007; Otomo et al., 2012). The gene discussed is ALS2; the disease is hereditary spastic paraplegia.