Comparison of LacZ staining in arteries from vWF-LacZ knockin mice with or without native or heterologous intron. Organs were harvested from 6- to 8-week-old male mice and processed in parallel for whole-mount staining with X-Gal. Shown are the basilar artery (thick arrow), middle cerebral artery (thin arrow), and internal thoracic artery (asterisk) from vWF^LacZ/+ mice (A, B, and C, respectively), vWFΔInt^LacZ/+ mice (D, E, and F, respectively), vWFGIn^LacZ/+mice (G, H, and I, respectively), vWFDIn^LacZ/+ mice (J, K, and L, respectively) and vWFHIn^LacZ/+ mice (M, N, and O, respectively). Note the reduced LacZ staining in basilar artery, middle cerebral artery, and internal thoracic artery from vWFHIn^LacZ/+ mice. Whole-mount tissues were analyzed under a Nikon SMZ-U dissecting microscope, and microphotographs were collected using a Nikon Coolpix 8400 camera.