Expression patterns of CDX2 and ACE in the mouse and human AGM region. (A) Representative cross sections through the aorta (Ao) of 34-day human embryos (Carnegie stage [CS], 15) (n = 3) and E10.5 mouse embryos (36 somite pairs) (n = 4), immunostained with anti-CD34, anti-CD31, anti-CDX2, and anti-ACE antibodies (brown staining). All intra-aortic hematopoietic cluster (IAHC) cells (black arrowhead) stained by CD34 (for human) and CD31 (for mouse) express ACE, which is also expressed by the endothelial cells underlining the ventral side of the aorta (white arrowhead). Transcription factor CDX2 is expressed by the hematopoietic cell of the intra-aortic clusters. Scale bars represent 10 µm. (B) Representative images of CDX2 RNASCOPE in situ hybridization in cross sections of the aorta (Ao) of 36-day human embryos (CS, 15) (n = 4) and E10.5 mouse embryos (n = 5) (brown staining). CDX2 mRNA is detected in hematopoietic cell clusters (black arrowheads), in some endothelial cells (white arrowheads), and in rare mesenchymal cells (stars). Scale bars represent 10 µm. Higher magnification views of highlighted regions are shown below each figure. (C-D) RT-qPCR analysis of ACE (C) and CDX2 (D) expression in IAHC cells, endothelia cells (EC), and mesenchymal cells (MC) isolated from E10.5 and E11.5 murine AGM. Results are normalized to glyceraldehyde-3-phosphate dehydrogenase (Gapdh), and expressed relative to the E10.5 AGM samples. Values are represented as mean plus standard error of the mean (SEM) (n = 7). *P < .05, **P < .01, ***P < .001, ****P < .0001.