KLF4 and amyotrophic lateral sclerosis: Skin fibroblast samples from sALS patients and from a non-neurological controls were collected in the UPMC ALS Center, and reprogrammed with lentivirus carrying KLF4, SOX2, OCT4 and cMYC44 to generate iPSCs with classic morphological features of a stem cell colony including small tightly packed cells with low cytoplasmic-to-nuclear volume ratio and tight borders (Supplementary Fig. 1a).