CFU-S-11 activity does not localize solely with the aorta in the aorta-gonad-mesonephros region

The aorta-gonad-mesonephros (AGM) region is a potent hematopoietic site in the midgestation mouse conceptus and first contains colony-forming units-sp leen day 11 (CFU-S-11) at embryonic day 10 (E10), Because CFU-S-11 activity is present in the AGM region before the onset of hematopoietic stem cell ( HSC) activity, CFU-S-11 activity in the complex developing vascular and uro genital regions of the AGM was localized. From E10 onward, CFU-S-11 activit y is associated with the aortic vasculature, and is found also in the uroge nital ridges (UGRs), Together with data obtained from organ explant culture s, in which up to a 16-fold increase in CFU-S-11 activity was observed, it was determined that CFU-S-11 can be increased autonomously both in vascular sites and in UGRs. Furthermore, CFU-S-11 activity is present in vitelline and umbilical vessels. This, together with the presence of CFU-S-11 in the UGRs 2 days before HSC activity, suggests both temporally and spatially dis tinct emergent sources of CFU-S-11. (Blood, 2000;96:2902-2904) (C) 2000 by The American Society of Hematology.