Suz12^Plt8/+ pro-B cells have enhanced self-renewal potential. (A) Limiting dilution analysis of Suz12^+/+ (n = 8) and Suz12^Plt8/+ (n = 4) bone marrow cells was performed to compare the frequency (f) of B-lymphoid progenitors. Cells were cultured on OP-9 stroma with IL-7. The clonogenic cell frequency model fitted to each dilution series is shown by a solid straight line relating the log₁₀ fraction of negative wells to the number of cells per well. Steeper slopes indicate higher frequencies of colony-forming cells. Broken lines show 95% confidence intervals. (B) Unfractionated bone marrow cells from 3-week-old Suz12^+/+ (n = 6) and Suz12^Plt8/+ (n = 5) mice were cultured in methylcellulose with IL-7, and the numbers of colonies were scored 7 days later. Data represent means ± standard error of the mean (SEM). A 2-tailed Student t test was performed (*P < .05). (C) Limiting dilution analysis showed no difference in progenitor frequencies of purified bone marrow pro-B cells (B220⁺CD19⁺c-Kit⁺IgM⁻) from 3-week-old Suz12^+/+ and Suz12^Plt8/+ mice. (D) Self-renewal potential of Suz12^+/+ (n = 8) and Suz12^Plt8/+ (n = 8) pro-B cells was determined by serial replating of colonies in methylcellulose. Data represent means ± SEM. A 2-tailed Student t test was performed (*P < .05; ***P < .001). (E) Comparison of the clonogenic potential of individual primary colonies from Suz12^+/+ and Suz12^Plt8/+ pro-B cells, expressed both in frequency and total secondary colony numbers. Data represent means ± SEM. A 2-tailed Student t test was performed (**P < .01; ***P < .001).