CreERT2-p53^F/F and CreERT2^+/F mice display efficient p53 allele excision in many tissues after tamoxifen treatment.

<p>(A) Experimental design to generate mice that can inducibly and somatically delete p53 in many tissues. Floxed p53 alleles are represented by triangle flanked bars. Cre-excised p53 alleles are indicated by solo triangles. (B) Tamoxifen treatment of wildtype mice moderately elevates liver DNA mutation frequency. Three month C57BL/6 Big Blue Mice designed to measure mutation frequencies were treated with tamoxifen (five 1 mg daily injections) and sacrificed at 2 or 4 weeks post-injection and liver DNA subjected to the mutation frequency assay as described in the <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0006654#s4" target="_blank">methods</a>. Mutation frequencies are shown with or without tamoxifen injection (n = 3 for each time point, ±standard error of the mean). (C) Tamoxifen injection of mice has little or no effect on survival compared to vehicle-injected wildtype mice. Tamoxifen injection of CreERT2 negative p53^F/F and p53^+/F mice (red curve, n = 23) showed similar Kaplan-Meier survival curves as wildtype uninjected mice (black curve, n = 55) and vehicle injected CreERT2-p53^+/F mice (blue curve, n = 50). (D) PCR assays show that vehicle-injected CreERT2-p53^+/F tissues exhibit no p53 allele excision, while all tamoxifen-injected CreERT2-p53^+/F tissues show evidence of p53 allele excision. Upper panels show genotyping PCR where the upper band (F) is the larger non-excised floxed allele of p53 and the lower band (+) is the non-floxed wild type p53 allele from various CreERT2-p53^+/F tissues. The lower panels show PCR fragments specific for the excised p53 allele (Δ). The left set of panels contain results from vehicle (corn oil) treated tissues while the right set of panels contain PCR results from tamoxifen treated tissues. Note that in the absence of tamoxifen there is no background p53 allele excision and that in the presence of tamoxifen all tissues show evidence of p53 allele excision. (E) Tamoxifen treatment of CreERT2-p53^+/F and CreERT2-p53^F/F mice results in efficient p53 allele excision (Δ) in some, but not all tissues. Southern blot analysis of genomic DNA from various CreERT2-p53^+/F and CreERT2-p53^F/F tissues was performed as described in the <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0006654#s4" target="_blank">methods</a>. Note that spleen and liver show efficient excision, lung and kidney show partial excision, while eye and brain show little evidence of excision.