Fig. 3

Ultrastructure of the eye region in 5-day-old wild-type (WT; A,D) and the N-cadherin pac^paR2.10 mutant (B,C,E) zebrafish. A: WT photoreceptor cells (example outlined) form membranous discs (MD) in the outer segment, partially surrounded by the pigment epithelium (PE). The inner segment or ellipsoid (EL) contains numerous mitochondria, and the nuclei (N) form the outer nuclear layer. B: The electron photomicrograph depicts a disturbed area of the outer mutant retina, including part of the pigment epithelium. In the mutant, photoreceptor cells are often not properly arranged in parallel like in WT. Photoreceptor orientation is sometimes even inverted, so that the nucleus lies closer to the pigment epithelium than the rest of the cell (cell labeled with N and EL; the MD segment is not in plane with the section). The (outer) plexiform layer (PL) comes close to the pigment epithelium, only separated by one row of nuclei. The mutant pigment epithelium cells are indistinguishable from WT. C: This electron photomicrograph depicts part of a rosette formed by photoreceptors similar to the one shown in Figure 2B. Note that although some photoreceptor cells are deformed (see also leftmost photoreceptor in B), a membranous disc segment and a segment containing mitochondria are formed like in WT. D: WT inner plexiform layer. E: Mutant inner plexiform layer island (of a rosette like shown in Fig. 2F). The number and morphology of synapses (arrows and insets) is indistinguishable between WT and mutant. Original magnifications = ×4,000 in A-C, ×30,000 in D,E, ×56,000 in insets.