ES cells and iPSCs were cultured in ESC media containing 15% FBS, and 1,000 U/ml of LIF. For the reprogramming of somatic cells, retrovirus expressing Oct4, Sox2, Klf4, and Myc were introduced. For the somatic cells containing inducible reprogramming factors, the media was supplemented with 2 ng/ml of doxycycline. For DNA and RNA isolation, fESC or iPSCs were trypsinized and re-plated onto new tissue culture dishes for 45 minutes to remove feeder cells, and nucleic acids were extracted from the non-adherent cell suspension. Genomic DNA methylation analysis and pyrosequencing were performed by previously published methods2021.
