HSC exhaustion in Pot1b^Δ/Δ;mTerc^+/− mice precedes BM failure. (A) FACs analysis of multilineage negative population in aging Pot1b^Δ/Δ; mTerc^+/− mice. Numbers are the percentage of LSK and LK cells in total BM. Each age group represents a minimum of 4 mice. Lin−: muiltilineage negative. (B) BM morphology in the diaphysis of the bone of wild-type and Pot1b^Δ/Δ; mTerc^+/− mice at the indicated ages (×20 magnification). Each image corresponds to the above flow cytometric analysis. (C) Quantification of total BM nucleated cell counts for wild-type (WT) and Pot1b^Δ/Δ; mTerc^+/− mice at the indicated ages. Each age group represents a minimum of 4 mice. Error bars represent SEM.