Iizuka K, Yokomizo T, Watanabe N, Tanaka Y, Osato M, Takaku T, Komatsu N (2016) Lack of phenotypical and morphological evidences of endothelial to hematopoietic transition in the murine embryonic head during hematopoietic stem cell emergence. PLoS One 11:e0156427. doi: 10.1371/journal.pone.0156427
Summary: Hemogenic endothelial cells have been observed in several embryonic tissues, such as the dorsal aorta, the placenta and the yolk sac. Recent work also suggest that the mouse embryonic head also produces hematopoietic stem cells (HSCs)/progenitors. However, a histological basis for HSC generation in the head hasn’t been determined because the hematopoietic cluster and hemogenic endothelium have not been well characterized. The authors in this study used whole-mount immunostaining and 3D confocal reconstruction techniques to analyze both c-Kit hematopoietic cluster and Runx1 hemogenic endothelium in the whole-head vasculature. Alexa488 labeled anti-NGFr (Cat. #FL-N01AP) was used in flow cytometry. The number of c-Kit hematopoietic cells was 20-fold less in the head arteries than in the dorsal aorta. In addition, nascent hematopoietic cells, observed by a budding structure and a Runx1 hemogenic endothelium, were not observed in the head. These results suggest that head HSCs may not be or are rarely generated from the endothelium in the same manner as aortic HSCs.