We counted iPSC colonies after a single dose of 3 Gy irradiation on days 1–6 post-infection when using an iPSC generation assay with Nanog-GFP MEFs infected using Yamanaka 4 factors, Oct3/4, Sox2, Klf4, and c-Myc expressed in retroviral vectors19,20. This evidence concerns the gene NANOG and infection.