Universal loss of cells with the Mdm2+/−Mdm4+/− genotype in the developing embryos. (A) A schematic diagram of generating the mosaic embryos. BW, body weight. (B) Whole-mount X-Gal staining of the embryos 36 h after tamoxifen injection (E6.5). Embryonic tissues were marked by dotted lines. (Scale bars, 1 mm.) (C) X-Gal staining of heart, kidney, liver, and lung from E19.5 UBC-creERT2; Rosa-lacZ; Mdm2flox/+ (M2f/+) and UBC-creERT2; Rosa-lacZ; M/M embryos. (Scale bars, 100 μm.) (D) QRT-PCR analysis of LacZ levels from tissues of E19.5 UBC-creERT2; Rosa-lacZ; Mdm2flox/+ (M2f/+) and UBC-creERT2; Rosa-lacZ; M/M embryos (n ≥ 3). Data are presented as mean ± SD. **P ≤ 0.01; ***P ≤ 0.001 (two-tailed t test).