Fig. 2

Histological eye sections at different developmental stages. Comparisons of (A–E) wild-type sections with (F–J) mutant sections show a progressive morphological deterioration in the outer layer of the retina. At 3 dpf, the RPE appears to be lighter pigmented in (F) fdv mutants than in (A) wild-type larvae. (B and G) Sections taken from 5-dpf-old larvae show a thickening of the RPE in the mutant larvae, (arrowheads in G) the appearance of pigment clots in the RPE and a reduced length of the outer segments in fdv mutants, while the (B) wild-type RPE is densely pigmented and microvilli of the RPE interdigitate with the PRC outer segments. In sections of (H) 7 dpf fdv larvae, the RPE is even more severely affected. The RPE cells are lighter pigmented in the mutant, containing pigment clots and no microvilli. PRC outer segments are bent sideways, as can be seen at higher magnification ((D) wild-type and (I) fdv mutant) and (arrowhead in panel I) are even absent in some parts of the mutant retina. Surprisingly, a comparison of sections of (J) adult fdv mutant and (E) wild-type eyes shows that the RPE and the PRC outer segments have recovered in the mutant, and (arrowheads in panels E and J) microvilli interdigitating in between the outer segments of PRCs can be seen. The inner retina is not affected at any of the developmental stages examined. ON, optic nerve, GCL, ganglion cell layer, IPL, inner plexiform layer, INL, inner nuclear layer, OPL, outer plexiform layer, ONL, outer nuclear layer, OS, outer segments, RPE, retinal pigment epithelium. Scale bars in panels (A–C), (F–H), (E) and (J) are 50 mm. Scale bars in panels (D) and (I) are 20 mm.