To achieve this goal, we reprogrammed 12 different established MEF cell lines into induced pluripotent stem cells (iPSCs) through retroviral transduction of the pluripotency factors OCT4, SOX2, and KLF4, and 20 days post-infection, we stained the resulting colonies, without observing any significant difference between both genotypes (Figure S4). This evidence concerns the gene SOX2 and infection.