Article Figures & Data
Figures
- Figure 2.
Development of photoreceptor pattern after removal of the distal tip of the optic vesicle. A pie fragment of the right optic vesicle was removed at its distal tip (A, B). The distribution of rods at E18 of this embryo is shown after in situ hybridization with a rhodopsin probe. C, Left, Control retina. D, Right, Operated retina. The arrows in C and D indicate the central rod-free zone, and the arrowheads indicate the horizontal rod-sparse streak. E, F, Higher magnification of the area centralis of the above retinas of the left (E) and right eye (F). G, H, Onset of expression of red cone opsin in the control (G, left) and experimental (H, right) retinas at E14 in another specimen, in which the same surgery was performed. (The images of the left retinas were mirrored so that, in all panels, dorsal is to the top, ventral is to the bottom, nasal/anterior is to the right, and temporal/posterior is to the left.) Scale bars, 3.75 mm.
- Figure 1.
EphA3 expression profile after partial resection of the anterior optic vesicle. A, Schematic of the performed surgery. B, The actual ablation of the specimen. Most of the right anterior optic vesicle was removed in ovo at HH stage 11. C, D, Expression of EphA3, as visualized by in situ hybridization, in the control (C, left) and operated (D, right) retinas at E7 of the specimen shown in B. (The image of the left retina was mirrored so that, in all panels, dorsal is to the top, ventral is to the bottom, nasal/anterior is to the right, and temporal/posterior is to the left.) Scale bar, 1.5 mm. E, Higher magnification of the boxed area in D, demonstrating clusters of EphA3-expressing and -nonexpressing cells.
- Figure 3.
Distribution of rod photoreceptors after ablation of the anterior optic vesicle. Most of the anterior optic vesicle was removed at HH stage 11 (A, B). The rod distribution was severely altered in the operated retina (D, right) when compared with the control (C). The density of rods in the dorsal and ventral areas of both retinas are shown below at higher magnification (E-H). The regions from which the pictures were taken are marked by boxes: E, F, higher magnification of the control and left retina on the dorsal (E) and ventral (F) sides; G, H, higher magnification of the operated right retina dorsally (G) and ventrally (H). (The image of the left retina was flipped so that, in all panels, dorsal is to the top, ventral is to the bottom, nasal/anterior is to the right, and temporal/posterior is to the left.) Scale bars, 3 mm.
- Figure 4.
The influence of partial optic vesicle ablation on retinal DV pattern. A-C, cVax expression after removal of the anterior eye anlage. The surgery was performed at HH stage 11 (E1.5; A). At HH stage 16 (E2.5), the expression domain of cVax was indistinguishable in the left control eye (B) and right operated eye (C) of the specimen shown in A. D-F, cVax expression after removal of the dorsal optic vesicle. The ablation was performed at HH stage 11 (D). After 24 h (at HH stage 16), the operated right eye was often smaller in size (F) than the left control eye (E) and showed ectopic expression of cVax in the dorsal eye cup (F, arrowhead). G-I, Distribution of rods after removal of the dorsal eye anlage. Ablation of the dorsal optic vesicle at HH stage 11 (G) caused a clear ventralization of the rod pattern at E18 (H, I). In the left control retina, the rod-free zone (arrow) and rod-sparse streak (arrowhead) were visible (H). In the right operated retina, both structures were missing, and the normal ventral domain of high rod density extended across the entire retina (I). In H and I, remnants of the pigment epithelium still attached to the neural retina are visible. (The image of the left retina was flipped so that, in H and I, dorsal is to the top, ventral is to the bottom, nasal is to the right, and temporal is to the left.) Scale bars, 3 mm.
- Figure 5.
Rod distribution after forced expression of FoxG1, GH6, and SOHo1. A-D, Representative examples of the rhodopsin distribution in E18 retinas, in which the expression of the molecules indicated was artificially raised across the entire retina. The rod pattern after retroviral misexpression of FoxG1 (B), GH6 (C), or SOHo1 (D) does not differ from the pattern observed in control retinas, which were infected with a control virus expressing alkaline phosphatase (A). In the inset in D, a representative retina infected with RCAS-SOHo1 was harvested at E7 and stained with a probe specific for the viral gag gene, indicating high and uniform infection during the peak period of photoreceptor genesis in the chick. (In all panels, dorsal is to the top, ventral is to the bottom, nasal/anterior is to the right, and temporal/posterior is to the left). Scale bars, 3 mm.
- Figure 6.
Photoreceptor distribution after forced expression of cVax or a putative dominant-negative form of Tbx5. A, Distribution and spacing of rods in an uninfected control retina at low magnification. Boxes indicate the regions shown at higher magnification in B-D: the rod-free zone in the central retina (B) and dorsal-temporal (C) and ventral-temporal (D) areas. E-H, Representative results obtained after retroviral misexpression of cVax: the rod-free zone did not form, the overall rod distribution was disturbed, and patches of high-rod density were scattered across the retina. F-H show the randomization of the rod distribution in higher magnification. The regions from which the pictures were taken are indicated by boxes in E. Cones expressing green opsin are evenly distributed along AP and DV axes (I). Ectopic cVax expression under similar conditions as used for E-H did not affect this pattern (K). J, L, Higher-magnification views of two additional examples: green cones of an uninfected control (J) and RCAS-cVax infected experimental retina (L) were evenly spaced. M-P, Representative results observed after ectopic expression of Tbx5-EnR. N-P, High-magnification images of the areas marked by boxes in M showing irregular spacing of rod photoreceptors. The inset in M shows the degree of infection with RCAS-Tbx5EnR in the retina depicted in M, visualized by two-color in situ hybridization as described by Schulte and Cepko (2000), with detection of the rhodopsin transcripts in dark blue and the viral RNA in pink. (In all panels, dorsal is to the top, ventral is to the bottom, nasal/anterior is to the right, and temporal/posterior is to the left.) Scale bars, 3.75 mm.
- Figure 7.
Altered rod distribution after resection of the anterior eye anlage. A, The optic vesicle, schematically represented as circles, is polarized along the AP of the vesicle by several known and unknown factors. Anterior positional values are indicated by a yellow gradient, and posterior values are indicated by a blue gradient. Along the DV axis, the eye anlage is separated into the domains of expression of cVax ventrally (green) and Tbx5 dorsally (pink). Cells along the horizontal meridian of the optic vesicle express neither molecule. The normal rod pattern develops under the influence of these factors. B, Removal of the anterior eye anlage will leave a remnant of the optic vesicle behind of almost maximal posterior characteristics. These cells can only give rise to the posterior-most aspect of the rod pattern. C, When the optic vesicle reconstitutes by proliferation of the remaining cells, the cells appear to retain the positional information they had before the surgery. Consequently, the vesicle remnant gives rise to a retina in which the rod distribution resembles a repetition of the most posterior aspect of the pattern: a dorsal shift of the rod-rich ventral domain containing arod-sparse streak but no rod-free zone. D, Removal of the dorsal optic vesicle leaves a ventral remnant of the vesicle behind. E, After reconstitution, the healed optic vesicle is entirely composed of cells of ventral origin. Hence, the retina developing from such a vesicle is ventralized with respect to the rod distribution. F, Retroviral misexpression of cVax generates random patches of ectopic cVax expression scattered across the optic vesicle and thereby creates numerous new boundaries between cells expressing high levels of cVax and cells not expressing cVax. This leads to an altered distribution of rods across the retina.
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