Telomere maintenance in purified stem cell-enriched Fancg^-/- hematopoietic cells. (A) Telomere restriction fragments (TRFs) of hematopoietic cell populations progressively enriched for stem cells. Pooled low-density mononuclear cells (LDMNCs) were obtained (3 per genotype), and Lin^- cells were isolated from the pooled cells and run on the same blot for comparison. Loading, 50 000 cells per lane. (B) Q-FISH analysis of pooled LDMNCs and Lin^-/- wild-type and Fancg^-/-. The average telomere length for each histogram is shown as a vertical line; deviation to the right in the Lin^-/- populations of both genotypes indicates increased telomere reserve compared with the more differentiated LDMNCs. (C) To study whether telomere shortening with differentiation was homogeneous in all telomeres independent of their length, we calculated telomere length differences (Δtelomere length) between Lin^- and LDMNCs for the 10th, 25th, 50th, 75th, and 90th percentiles. Although telomeres were longer in the Lin^- population at all percentiles and independent of the genotype, telomere loss with differentiation was significantly greater in the higher percentiles compared with the lower, indicating preferential maintenance of short telomeres with differentiation in both wild-type and Fancg^-/- cells.