The cre gene is expressed in CD34-tTA/Tet-O-cre double-transgenic mice in a manner similar to that of human CD34.

(A) Northern blot analysis demonstrates that a functional transactivator protein is expressed in the heart, lung, and lymph nodes of double-transgenic animals as indicated by the expression of cre RNA. The blot was stripped and rehybridized to human CD34, which is part of the transgenic construct (Figure 6) and demonstrates a similar expression pattern, and then to murine GAPDH. (B) Expression analysis with RT-PCR confirms expression of cre in bone marrow, liver, and thymus. (C) Multiplex real-time PCR with amplification of 18S RNA in the same tube as cre was performed for relative quantitation of expression levels among different tissues. The top graph shows the curves for amplification of the cre gene, whereas the bottom graph demonstrates equal amounts of cDNA in all samples as determined by amplification of 18S RNA. (D) Expression levels of cre RNA relative to 18S within different tissues calculated based on results shown in panel C. Expression in liver, which showed the lowest levels, was arbitrarily assigned to a value of 1.