Cell-cycle analysis of the HSC-enriched fraction of W41/W41 fetal liver cells. Isolation of viable, lin−Sca1+CD43+E14.5 fetal liver cells from W41/W41 mice (left panel) that were then further enriched for HSCs by isolation of the Mac1+ subset and their distribution in G0/G1 versus S/G2/M assessed by staining with Hoechst 33 342 (right panel). Data are representative of 2 independent experiments.