Ews deletion accelerates cellular senescence from prenatal stages and leads to a significant decrease in BM cellularity. (A) The mononuclear cells from normal adult mice were sorted based on lineage marker expression. Antibodies to B220, CD3, and CD11b were used to enrich B (from spleen), T (from thymus), and myeloid (from BM) lineages, respectively. Lineage-negative (Lin⁻) and positive (Lin⁺) BM cells were enriched by magnetic separation. Lin⁻ cells were further fractionated on the basis of Sca1 expression (Lin⁻ Sca1⁺). The purity of the sorted populations was > 92%. Quantitative RT-PCR was performed as described in “Quantitative real-time PCR.” Expression was normalized to the endogenous Gapdh. The fold difference in expression of Ews was calculated using the ΔΔCt method. CD11b⁺ cells, where the lowest Ews expression was detected, was set arbitrarily as 1.0. Data are presented as mean values ± SD. (B) Embryos (E16.5-E18.5) were collected from pregnant dams and stained for SA-β-gal. Pictures show representative embryos from 3 additional independent experiments. (C) BM cells from Ews^+/+ and Ews^−/− mice were harvested during the postnatal period. Total nucleated BM cellularity was determined by hemocytometer counting from birth through postnatal day (PND) 28. **P = .0075 by 2-tailed Student t test.