Simultaneous tracing of HSC proliferation and differentiation. Adult Pdzk1ip1-CreER R26^SW reporter mice were given a single dose of tamoxifen and analyzed for the expression of Tom (preexisting) and GFP (Cre induced) at the start of labeling by BM biopsy and/or at the 1-wk endpoint. (A) The expression of Tom and GFP among total BM cells in a control Cre-negative animal or in a reporter animal at the start of labeling (by biopsy) and after 1 wk. Different levels of Tom expression among GFP⁺ cells are highlighted. Representative of three animals. (B) The phenotype of gated Lin⁻ GFP⁺ cells expressing different levels of Tom (high, low, or negative) as indicated in A. (C) The phenotype of gated Lin⁻ c-Kit⁺ Sca-1⁻ progenitors, either total or GFP⁺ 1 wk after labeling. Representative of five animals; pooled statistics are shown in Fig. S2 A. (D) Representative profile of Tom fluorescence in GFP⁺ cells 1 wk after labeling, with distinct peaks of Tom expression highlighted. (E) The fraction of cells within each peak of Tom expression among GFP⁺ cells (mean ± SD of five animals). (F and G) The phenotype of GFP⁺ cells within each peak of Tom expression. Shown are the fractions of each phenotypic population within each peak (F; mean ± SD of five animals) and representative flow cytometry profiles of cells within each peak (G).