Fig. 3. Anxa5-lacZ⁺ cells are found associated with, but are not identical to, the endothelium in capillaries of E10.5 embryos and adult vasculature. (A) Sagittal sections of heterozygous embryos at E10.5 were stained for lacZ activity and immunostained for PECAM. After merging, Anxa5-lacZ⁺ regions appear red (arrows). Anxa5-lacZ⁺ cells are located parallel to the lining endothelial cells. (B) Ultrastuctural localization of Anxa5-lacZ⁺ expression in heterozygous embryos at E10.5 by electron microscopy. An electrondense deposit of X-gal product is detected (arrow) exclusively in PVCs. (C,D) Sections from adult kidney tested for lacZ activity (C) and SMA expression (D) showed colocalization in the vascular walls of large blood vessels. The relative intensity of fluorescence was reduced by X-gal staining. (E) Expression of the Anxa5-lacZ reporter in brain of adult mice is found in the pial vasculature. (F) X-gal staining (arrow) is restricted to cytoplasmic vesicles in pericytes, characterized by the common basement membrane (arrowhead) with endothelial cells. Capillaries (C), endothelial cells (EC) and pericytes (P) are marked (B,F). Scale bars: 50 µm (A,C); 1 mm (E).