Tie2 and GATA1 expression in transgenic mice. β-Galactosidase activities driven by the transgene recapitulate endogenous Tie2 and GATA1 protein expression, respectively, in the Tie2-LacZ and GATA1-LacZ transgenic mice. ex indicates extraembryonic region; em, embryonic region. Note that the pattern of Tie2 expression visualized by β-gal activity is similar to the pattern observed after immunohistochemical analysis using an anti-Tie2 antibody. Scale bars indicate 50 μm. All images were captured with a Leica DC500 CCD camera with IM50 Imaging Manager through a Leica MZ FLIII microscope using a PLAN APO 1.0×/0.125 lens (final magnification, ×32 for embryos at somite stages; ×40 for embryos at headfold stages; and ×63 for embryos at streak and neural plate stages).