Kras ^G12D -mutant HSC show accelerated multilineage contribution. HSC-specific Cre reporter mice (Pdzk1ip1-CreER R26^Tom/Tom) that carried WT or conditional mutant (Kras^G12D) Kras alleles were administered a single dose of tamoxifen to induce simultaneous Tom expression and Kras mutation in HSC. (A) Schematic of the alleles and their recombination following tamoxifen administration. The transcriptional stop cassettes containing polyadenylation signals (STOP/pA) and the LoxP sites (green triangles) are shown. For the endogenous Kras alleles, the WT, the conditional unrecombined LSL, and the recombined mutant (G12D) alleles are shown. (B) Recombination of conditional Kras allele in Tom⁺ or Tom⁻ LSK cells sorted from the BM 3 wk after tamoxifen treatment. The left panel shows genomic PCR results for two independent animals, with the amplicons for Kras alleles (A) and sizes of DNA size markers (in base pairs) indicated. The right panel shows densitometric ratios of the recombined (G12D) to unrecombined (LSL) amplicons. Symbols represent individual mice; bars represent the mean ± range. (C) Kaplan–Meier plot of animal survival over the indicated time after tamoxifen administration (n = 16 for Kras^G12D and 12 for WT mice). (D) Lineage tracing of Kras^G12D-mutant HSC. Reporter mice were monitored for Tom expression in PB every 4 wk for up to 12 wk. (E) Accrual of Tom⁺ cells in the blood. Shown are fractions of Tom⁺ cells within the indicated blood cell types in Pdzk1ip1-CreER R26^Tom/TomKras^G12D or WT reporter mice after tamoxifen treatment. Symbols represent the mean ± SD of five to six mice per group. (F–H) Analysis of reporter mice at the indicated endpoint. Shown are the fractions of Tom⁺ cells within immune cell types in the spleen (F) and the BM (G), and within subsets of thymocytes (H). Symbols represent individual mice; bars represent the mean ± SD of data from a single experiment (weeks 2–3) or from two experiments (week 5). Statistical significance was estimated by the Mantel–Cox test (C) or the Mann–Whitney test (other panels). *P < 0.05, **P < 0.01, ***P < 0.001. Source data are available for this figure: SourceData F1.