Fig. 1. Expression of Notch family members in the endothelium of the P-Sp/AGM aorta. (A) E9.5 embryo, indicating the site for P-Sp/AGM aorta and hematoxilineosin staining of a transverse section at the indicated level (100x) (B,C,D) Whole-mount of (B) Notch receptors, (C) Notch-ligands and (D) Notchtarget genes and transverse sections of E9.5 and 10.5 aortas. (B) Notch1 is expressed in few scattered cells at E9.5 and these cells increase at E10.5. Notch2 and Notch3 are not expressed in the aorta. Notch4 shows a homogenous staining pattern in most of the cells of the endothelium at E9.5 and 10.5. (C) Dll1 and Dll3 are not expressed in the aorta. Jag1, Jag2 and Dll4 are expressed in few scattered cells at E9.5 and these cells increase at E10.5 (D) Hes1 is not expressed at E9.5 but shows expression at E10.5 in cells budding from the endothelium. Hrt1/herp2 is expressed in the ventral endothelium and hematopoietic clusters at E9.5 and 10.5. Hrt2/Herp1 shows more diffused expression at E9.5 and ventral endothelium at E10.5. Orientation of the aortas is dorsal (up) to ventral (down).