POU5F1 and amyotrophic lateral sclerosis: Totally 6 iPS cell lines were generated by retroviral expression of mouse Oct4, Sox2, c-Myc, and Klf4 from B6SJL-TgN TTFs and C57BL/6 TTFs for characterization and comparison, in which 3 iPS cell lines were derived from 3 transgenic B6SJL-TgN mice (ALS-iPS) and 3 iPS cell line were derived from 3 C57BL/6 mice (C57-iPS) (Figs. 1A and 1C).