Fig. 2. Ventral eye abnormalities in embryos injected with RCAS-noggin at HH stages 15-18. (A-D) Expression of viral gag proteins in eyes infected with RCAS-alkaline phosphatase or RCAS-noggin. Immunocytochemistry with AMV 3C2 antibody, which recognizes retroviral antigens, was carried out to monitor the extent of infection within each treated eye. Sections through eyes infected with alkaline phosphatase (A,B) or noggin (C,D) retrovirus showed infection throughout the retina, indicating that both retroviral stocks contained infective viral capsids. (E-J) Anatomical and histological features. E8, alkaline phosphatase controls (E-G) show a normally closed choroid fissure in the anterior segment of the eye (arrow, E), normal retina (F), and the presence of the pecten, depicted at both low (F, arrow) and high magnification (G, corresponding to boxed area in F). (H-J) Noggin-infected eyes showed lack of choroid fissure closure (colobomas; H, arrows). The pecten was undetectable in histological sections, and a large mass of mesenchymal-like tissue was noted in the ventral region of the optic cup (I, arrow; J is a higher magnification of the boxed region from I). (K,M) Internal aspect of the fundal region of eyes infected with alkaline phosphatase (K) or noggin (M), as seen after dissecting away the anterior region of the eye. An enlarged choroid fissure was found in noggin-infected embryos in the posterior chamber (M). The fissure was still present, but diminished, in the posterior pole of alkaline phosphatase controls (K). Noggin-infected embryos also showed a white fibrous material, projecting into the vitreal cavity of the eye (arrows, M). (L,N) Sections through the fundal region of alkaline phosphatase- (L) and noggin-infected (N) eyes, labeled with antibodies specific for class III ß-tubulin. Controls show darkly labeled ganglion cell axons at the vitreal edge of the retina, and into the optic nerve head (arrow, L). In noggin-infected eyes, in contrast, fibers were generally undetectable in the optic nerve but could be seen projecting into the vitreal chamber (arrow, N), corresponding to those in M. Scale bars: A-D, 50 µm; E,H, 500 µm; F,I, 500 µm; G,J, 50 µm; K,M, 500 µm; L,N, 500 µm.
