Frequency and expansion capabilities of CFU-F. (top) Frequency of CFU-F at the time of explantation (t0). Results shown as number of colonies per 105 nucleated bone marrow cells (mean of triplicate determinations per mouse). The tg marrow is reduced in CFU-F, relative to the wt marrow (analysis of variance [ANOVA], Scheffe's F test 309.16* [significant at 95%], P < 0.0001). (middle) Frequency of CFU-F at the end of ex vivo expansion (day 17, tN). Results shown as number of colonies per 103 stromal cells (mean of triplicate determinations per two cell strains per genotype). Strains of tg mice are enriched in total CFU-F, relative to strains of wt mice (ANOVA, Scheffe's F test 94.03* [significant at 95%], P < 0.0002). (bottom) Fold increase in CFU-F over the culture period was calculated as the ratio of the total number of CFU-Fs at the end of the culture period to the total number of CFU-Fs in the marrow explants. Results based on triplicate determinations in duplicate experiments (ANOVA, Scheffe's F test 124.52* [significant at 95%], P = 0.02). (top, middle, and bottom) Error bars indicate SD of the mean.