Enhancer activity of 5′ Int1 of the VECD gene in transgenic mice. Transgenic mouse strains harboring VECDp-EGFP or VECDp-5′ Int1-EGFP were established. (A) Histologic sections of the small intestine, retina, spleen, brain cortex, kidney, or heart were prepared from 8- to 10-week-old transgenic mice and were stained by anti-GFP antibody (green) and anti-PECAM-1 mAb (red). Two pictures are merged to show the specificity of expression. GFP expression was detected at varying extent in the small intestine, spleen, kidney, and heart of the VECDp-EGFP transgenic mouse, but not in the brain and retina of the same mouse. On the other hand, a high level of GFP expression was detected in all these organs of VECDp-5′ Int1-EGFP transgenic mice. Note, however, the presence of GFP^- PCAM-1⁺ cells in these tissues. Sagittal sections of E12.5 embryos were prepared from 2 stains of mouse, and expression of GFP and PCAM-1 was examined immunohistochemically. Arrows indicate the dorsal aorta. (B) E12.5 embryos of VECDp-EGFP or VECDp-5′ Int1-EGFP transgenic strains were collected, dissociated to single-cell suspension, stained by anti-VECD CD31 mAbs, and analyzed by FACS Vantage. Expression of VECD and GFP of the CD31⁺ population is presented.