Figure 2. Plasmid-mediated RMCE by transient transfection.

(A) Hygromycin-resistant colonies obtained upon transfection of HEK293A cells with the indicated plasmids containing the genetic landing pad (pKAS) or the transfer plasmid (pTRINA) expressing cre-recombinase at two different relative amounts (low and high [pTRINA]). Colonies were stained after ten days under conditions of selection. (B) Microphotographs under brightfields (left) and fluorescent light (right) of the transfected cultures with the indicated plasmids. (C) Number of cells expressing cherry fluorescent protein (ChFP+) upon RMCE on HEK293A cells measured by FACS analysis. Variable amounts of pKAS were used with a constant amount of pTRINA as is indicated. Transfections were made in duplicate, and the results shown in both A and B are from one representative experiment out of three.