Figure 2. Cdh23 transcripts are expressed in the zebrafish brain and retina. In situ hybridization showing cadherin 23 mRNA (mRNA) expression in the developing and mature zebrafish nervous system. A: Dorsal view of a zebrafish brain at 24 h postfertilization (hpf); the blue/purple signal shows the first detectable expression of cdh23 mRNA in two paired nuclei in the diencephalon, adjacent to the eye. B: Ventral view of intensely stained deep nuclei in the ventral diencephalon (vd) at 48 hpf. C: Lateral view of 48 hpf larva. The two most prominent nuclei labeled are located in the olfactory organ (oo) and the ventral diencephalon. Additional brain labeling is also observed, as is labeling of hair cells in the otic vesicle (ov). D: Sense control shows absence of nonspecific labeling. E: Dorsal view of the brain at 54 hpf, showing telencephalic and ventral diencephalic paired nuclei from a different angle, as well as additional dispersed cells in the mesencephalon and rhombencephalon. F: In the eye, a very small subset of inner layer cells is labeled. G-K: Post–in situ hybridization cryosectioning allowed the more accurate identification of labeled brain nuclei. Paired telencephalic nuclei were located just medial to the olfactory bulb (ob), in the subpallium (G). Caudal to the anterior commissure (ac), very intense labeling was found in bilateral bar-shaped structures in the eminentia thalami (EmT). H, I: Continuing caudally (J), bar-shaped nuclei became more globular in the ventral thalamus. Scattered labeling was also observed in the dorsal thalamus and points caudal in J-K. L: Blue lines represent planes of cryosections made in G-K. M: Cdh23 in situ hybridization in 6 weeks postfertilization (wpf) zebrafish shows ventral and dorsal thalamic labeling similar to that seen in larval stages, but is expanded to even more ventral areas, and to cells lying just ventral to the optic tectum (TeO). N, O: At 6 wpf and 6 months postfertilization (mpf), retinal labeling is still restricted to a very small subpopulation of amacrine cells. gcl, ganglion cell layer; inl, inner nuclear layer; ipl, inner plexiform layer; is, inner segment; onl, outer nuclear layer; opl, outer plexiform layer; os, outer segment. Scale bars=100 µm (G-K, M), 50 µm (N), 20 µm (O).