LMO2 proximal promoter directs endothelial expression in transgenic mice. E12.5 transgenic embryos expressing lacZ under the control of the LMO2 proximal promoter. (A) A representative embryo with endothelial staining discernible from whole-mount analysis and confirmed by histologic sections of a blood vessel (top right) and a capillary (bottom right). (B) The founder embryo with scattered β-galactosidase staining subsequently demonstrated to represent endothelial activity by histologic sectioning of the dorsal aorta (top right) and capillaries (bottom right). Whole-mount images were acquired using a Pixera Pro 150ES digital camera (Pixera, Los Gatos, CA) attached to a Nikon SM7800 microscope (Nikon, Kingston upon Thames, United Kingdom). Images of sections were acquired with the same camera attached to an Olympus BX51 microscope (Olympus, Southall, United Kingdom) using Olympus UPlanApo 40 ×/0.85 numeric aperture (NA) and 100 ×/1.35 NA objectives. ImagePro Express version 4.5 (Image Processing Solutions, North Reading, MA) was used for acquisition of both types of images. Digital images were processed using Adobe Photoshop (Adobe Systems, San Jose, CA).