Functional analysis of various promoters in lentiviral vectors at different stages of in vitro differentiation of mouse embryonic stem cells

Given the therapeutic potential offered by embryonic stem ( ES) cells, it is critical to optimize stable gene delivery and expression at different developmental stages of ES cell differentiation. Here, we systematically analyzed lentiviral vectors containing the following promoters: the human elongation factor 1 alpha ( EF1 alpha) promoter, the human cytomegalovirus ( CMV) immediate early region enhancer-promoter, the composite CAG promoter ( consisting of the CMV immediate early enhancer and the chicken beta- actin promoter), the human phosphoglycerate kinase 1 ( PGK) promoter, the murine stem cell virus ( MSCV) long terminal repeat ( LTR), or the gibbon ape leukemia virus ( GALV) LTR. Our results show that the EF1a promoter directed robust transgene expression at every stage of mouse ES cell differentiation, whereas the CMV promoter drove transgene expression only during late stages. Similarly, the CAG and PGK promoters drove transgene expression at a significant level only during late stages. The MSCV LTR and the GALV LTR exhibited much lower promoter activities at all stages. Interestingly, mouse ES cells transduced with the EF1 alpha promoter-containing lentiviral vector lost most of their transgene expression during in vitro differentiation to neural precursors and neuronal cells. Our results demonstrate that different cellular and viral promoters exhibit very distinct and dynamic properties not only in terms of promoter strength but also with respect to differentiation stage-specific activity.