H9 wa09 cells

The CRL2097 human fibroblast cell line was purchased from the American Type Culture Collection (ATCC, Rockville, MD, USA). CRL2097 cells were cultured in a human fibroblast medium consisting of MEM supplemented with 10% FBS and 1% sodium pyruvate (all purchased from Thermo Fisher Scientific, Waltham, MA, USA). H9 (WA09) cells were purchased from the WiCell Research Institute (Madison, WI, USA), and HUES9 cells were purchased from the Harvard Stem Cell Institute (Cambridge, MA, USA). Human embryonic stem cells (ESCs) and iPSCs were maintained in a pluripotent stem cell (PSC) medium consisting of TeSR-E8 medium (STEMCELL Technologies, Vancouver, Canada) supplemented with 1 mM nicotinamide (Sigma-Aldrich, St. Louis, MO, USA)^{27 (link)}. For subculturing, all PSCs were dissociated using Accutase (Millipore, Billerica, MA, USA) and then seeded onto plates coated with Geltrex (Thermo Fisher Scientific) in PSC medium containing 10 µM Y-27632 (Tocris, Bristol, England). The medium was replaced with PSC medium 16–24 h after passaging. All PSCs were passaged every 5–7 days. The ESCs used in this study were reviewed and approved by the Public Institutional Review Board designated by Ministry of Health and Welfare (P01-201409-ES-01). For reprogramming purposes, CRL2097 cells were exempted from IRB review (P01-201802-31-001).