Figure 5

Transfection of a bicistronic plasmid RFP-Cre led to transient expression of RFP and a stable expression of YFP. A: Co-expression of RFP with the Cre-induced YFP reporter gene was observed in virtually all the cells at 24 h after nucleofection, demonstrating that Cre-induced YFP expression faithfully reflected the pattern of nucleofection. Note that the level of RFP expression was variable among the cells, but that recombination was efficiently induced in all cells. Small arrowheads present cells expressing high level of RFP whereas big arrowheads present cells expressing a low level of RFP. Arrow highlights an YFP positive cell negative for RFP. B: Quantification of the number of RFP and YFP-positive cells at different time point post-nucleofection demonstrated the transient expression of RFP but persistent, long-term expression of the YFP reporter gene. Note that the efficiency of recombination using a bicistronic plasmid was similar to that achieved with monocistronic Cre nucleofection. C: At 14-days-post-transfection, only few cells still expressed RFP whereas the YFP induced expression remained stable.