Human skin fibroblasts NB1RGB [20–22 (link)] and human iPSCs 201B7 [23 (link)] were obtained from RIKEN Bio Resource Center. NB1RGB was maintained with Dulbecco’s Modified Eagle Medium and supplemented with 10% FBS and penicillin/streptomycin (Nacalai Tesque, Japan). iPSCs C2 were derived from NB1RGB by messenger RNA (mRNA) integration-free methods using the Stemgent® StemRNATM-NM Reprogramming Kit for Reprogramming Adult and Neonatal Human Fibroblasts (Stemgent, USA) as previously reported [11 (link), 24 (link)]. iPSCs were maintained as feeder-free culture with the NutriStem™ XF/FF medium (ReproCELL, Japan) and iMatrix511 silk (Nippi, Japan). NPCs were derived from iPSCs C2 using the PSC neural induction medium (Gibco, Thermo Fisher Scientific, USA) and maintained with the neural basal medium (Gibco, Thermo Fisher Scientific) and iMatrix 511 silk according to the manufacturer’s protocols with small modifications. iPSCs and NPCs culture media were supplemented with the Y27632 ROCK inhibitor (WAKO Pure Chemical Industries, Japan) during passage; on the subsequent day, the media were replaced with fresh culture media without the ROCK inhibitor.