BCL3 and infection: The expression levels of Bcl3 and Klf9 in ESCs were 30~150 folds higher than those in PGCs (Fig 1B), but OE resulted in much higher expression of Bcl3 and Klf9 (13,000~25,000 folds compared with control; S2A Fig), when we infected the virus vectors at the multiplicities of infection (MOI) 5.