GFP expression pattern in the Prox1-GFP BAC transgenic mice. (A) GFP expression in embryos and newborn mice: stereoscopic images of a Prox1-GFP (left) and a wild-type embryo (right) (E14.5) in the bright-field and green fluorescence channel (i-ii). (iii-v) A patch of Prox1-GFP embryonic back skin was peeled to visualize the dermal lymphatic network (v, enlarged image of the boxed area of subpanel iv). (vi) Leading front (arrows) of embryonic dermal lymphatic vessels. (vii-viii) Mesenteric lymphatic vessels and lymphatic valves (arrows) in a newborn mouse (P1). Bright-field and green fluorescent images of the embryonic liver (ix-x), the pancreas (xi-xii), the heart (xiii-xiv), the nervous system in the tail (xv-xvi), the eye (xvii-xviii), isolated eyeball (xix-xx), and the brain (xxi-xxii). Expression of GFP reporter in embryonic neural tube (xxiii), hepatocytes (xxiv), heart muscle (xxv), and intestine (xxvi) of newborn mice. (B) GFP expression in the Prox1-GFP BAC transgenic adult mice: bright-field and green fluorescent imaging allows a convenient distinction of transgenic (left) versus wild-type control (right) mice (i-ii). Cross sections of the eye lens (iii) and the retina (iv). Lymphatic vessels are shown in whole-mount preparations of the trachea (v), inner side of the skin (vi), ear edge (vii), Peyer patch (viii), mesentery (ix), surface of intestine (x) and lymph nodes (xi), diaphragm (xii-xiii), and an enlarged view (xiv) of boxed area in panel xiii. (xv-xvi) The ear of a Prox1-GFP mouse was wounded with an ear punch. *Lymphatic vessel regeneration was visualized at the edge of the wound at day 7. Filopodia of sprouting lymphatic endothelial cells are shown in a boxed area in panel xv and marked with arrows in the enlarged image (xvi). The thoracic duct of a Prox1-GFP mouse can be easily visualized in the retroperitoneal space (xvii) with an enlarged view (xviii). An isolated thoracic duct clearly shows a strong GFP positivity (xix-xx).