Expression of early markers of photoreceptor identity is reduced in cdh4 morphants. A-F: Zebrafish embryos were injected with either standard control morpholino oligonucleotide (MO, A,D) or cdh4 MO (B,C,E,F). crx (A-C) and otx5 (D-F) labeling in 78 hours postfertilization (hpf), embryos were used as markers of photoreceptor specification and differentiation. A,D: In controls, crx and otx5 labeling were confined to the photoreceptor layer and the outermost part of the inner nuclear layer. B,E: Some reduction of staining was seen in slightly affected cdh4 morphants. C,F: In severe cdh4 morphants, both crx and otx5 staining were reduced and lacked defined laminae.