Decrease in quiescent long-term repopulating (LTR)-hematopoietic stem cells (HSCs) and short-term repopulating (STR)-HSCs in ataxia telangiectasia mutated (ATM)−/−→ wild type (WT) mice. Cell cycle status for LTR and STR-HSCs was determined following staining with Pyronin Y and Hoechst blue. Top panel showing a pie chart for the percentage of LTR-HSCs in different stages of cell cycle; diabetes and ATM−/−→WT caused a significant decrease in quiescent (G0) LTR-HSCs with an increase in the numbers of cells in active cell cycle (G1 and G2). Bottom panel showing a significant lack in quiescent cells with an increase in cell numbers in the phase of the active cycle in all three groups except wild type (WT) animals. WT (n = 12), WT+ STZ (n = 5), ATM−/−→WT (n = 5), ATM−/−→WT (n = 5) Statistical test-one way analysis of variance followed by Student’s Newman Keul Test. Abbreviations: ATM, ataxia telangiectasia mutated; HSC, hematopoietic stem cell; LTR, long-term repopulating; STR, short-term repopulating; STZ, streptozotocin; WT, wild type.