iPS cells were generated with the EBV-based vectors as previously described16. Briefly, plasmids pEP4 EO2S ET2K (Addgene Plasmid 20927), pEP4 EO2S EN2L (Addgene Plasmid 20922), and pEP4 EO2S EM2K (Addgene Plasmid 20923) were transfected intohuman fibroblasts by Amaxa Nucleofector (Lonza; program U-023) at a concentration of 2 μg per 100 μl electroporation solution per 2 × 106 cells. Colonies of iPS cells were manually picked after 3–6 weeks for further expansion and characterization. Lack of vector integration was confirmed by qRT–PCR analysis as previously described16. Two lines from each individual that passed stringent criteria were used for the current study (Supplementary Table 1a). iPS cells (passage ≤ 35) were cultured on irradiated MEFs in human iPS cell medium consisting of D-MEM/F12 (Invitrogen), 20% Knockout Serum Replacement (KSR, Invitrogen), 2 mM L-glutamine (Invitrogen), 100 μM MEM NEAA (Invitrogen), 100 μM β-mercaptoethanol (Invitrogen), and 10 ng ml−1 human basic FGF (bFGF, PeproTech) as described16,31. For feeder-free culture of iPS cells, cells were cultured on Matrigel (BD Biosciences) with mTeSR1 media (Stem Cell Technologies). Media were changed daily and iPS cell lines were passaged by collagenase (Invitrogen, 1 mg ml−1 in D-MEM/F12 for 30 min at 37°C).
