Fig. 6. (A) VE-cadherin⁺CD45⁺ cells can be detected in all organs involved in the emergence (E12.5 yolk sac), migration (E12.5 blood) and expansion (E13.5 liver) of HSCs. The percentage of cells in each quadrant is indicated. Data are representative examples from six experiments. Each contour plot is composed from 1x10⁶ YS, 1x10⁵ (Ter119^-) PB and 3x10⁶ FL. Quadrants are based on appropriate isotype control staining (see Fig. S1 in the supplementary material). (B) Circulating double-positive cells of E12.5 peripheral blood show attenuated expression of endothelial markers. Each analysis was made using data from 80-110 DP, 1000-4000 endothelial or 8000-13,000 haematopoietic cells. (C) Within the E13.5 liver, some HSCs remain associated with the DP fraction. However, the majority of HSCs reside within the haematopoietic (VE-cadherin^-CD45⁺) fraction. This is reflected in the upregulation of essential stem cells markers (TIE2, KIT, SCA1 and MAC1) in the haematopoietic population. Each analysis was made using data from 1000-4000 DP, 8000-20,000 endothelial or 30,000-70,000 haematopoietic cells. All data are representative of 2-4 experiments for each marker analysed. Isotype control (white) and specific antibody staining (grey) are presented.