Cytotoxic stress exhausts the stem cell pool in <i>Inca1</i>-deficient bone marrow.

<p><b>A.</b> The Kaplan-Meier plot illustrates the survival of <i>Inca1^+/+</i> (n = 7) and <i>Inca1^−/−</i> (n = 13) mice after weekly administration of the myeloablative agent 5-fluorouracil (5-FU). 5-FU treatment targeted predominantly proliferating bone marrow cells and led to a significantly shortened lifespan of <i>Inca1^−/−</i> mice compared to their wild type littermates (p = 0.02, log-rank). <b>B.</b> Cell cycle analysis of total bone marrow from mice treated twice with 5-FU using BrdU/PI staining and subsequent FACS analysis. <i>Inca1^−/−</i> bone marrow cells of mice that had been exposed twice to 5-FU showed more cells in S-phase than 5-FU treated wild type mice. Shown here is a representative example of three independent experiments. <b>C.</b> Histological bone sections from 5-FU treated mice showed significant depletion of hematopoietic cells in the bone marrow of <i>Inca1^−/−</i> sternum (right-hand side) with replacement by fat cells compared to wild type control mice. In contrast, hematopoietic cell numbers were only mildly decreased in wild type mice (left panel). Lower panels show higher magnifications of the areas marked in the upper panels. <b>D.</b> The total number of nucleated bone marrow cells was significantly decreased in <i>Inca1^−/−</i> mice after two cycles of 5-FU treatment (mean ± SD, p = 0.002, t-test). All mice were 16 weeks old at the time of analysis. <b>E.</b> Bone marrow cellularity in non-challenged mice did not differ between <i>Inca1^−/−</i> and <i>Inca1^+/+</i> genotypes (mice aged 70 to 425 days; mean ± SD, p = 0.83, t-test).