Fig. 2

Fig. 2 The els mutant gene encodes PDE6α′. (A) Genomic region where the els mutation locus is mapped. The els mutational locus is mapped on chromosome 12 and flanked by two polymorphic markers, zC149K17-12 and zC149K17-3. Within this flanking region, there are three candidate genes, pde6α′ (Genbank Accession No. NW_00150719), rbp4 (Genbank Accession No. NM_130920) and a novel kinesin-like gene, ENSDAR000000009923 (Zebrafish genomic database of the Sanger Institute, Ensembl ver. 30). (B) A missense mutation (175Met->Arg) occurs in the GAF-A domain of PDE6α′ in the els mutant. (C) Amino acid comparison of a part of the GAF-A domain of pde6α′ gene between zebrafish and other vertebrate species including human (Genbank Accession No. NM_006204), mouse (Genbank Accession No. NM_033614), chick (Genbank Accession No. NM_204986) and frog (Rana pipiens, Genbank Accession No: AY044176). Three amino acids indicated in blue are important for the non-catalytic binding of cGMP to PDE6α′ (Huang et al., 2004). The position of Met-175 mutated in the els mutant is indicated by an asterisk and colored red. (D–F) Ventral views of 4 dpf zebrafish embryos labeled with RNA probes for pde6α′ (D), pde6α (E) and pde6β (F). The pde6α′ mRNA is expressed exclusively in the large region of the retina. The pde6α and pde6β mRNAs are expressed in the ventral patch of the neural retina, suggesting that these two genes are expressed later than the pde6α′ gene. (G–I) Plastic sections of 4 dpf zebrafish heads labeled with RNA probes for pde6α′ (G), pde6α (H) and pde6β (I). These mRNAs are expressed in the photoreceptor layers, suggesting that these genes are expressed exclusively in photoreceptors. (J, K) Sections of 6 dpf photoreceptor layers labeled with fluorescent-conjugated RNA probes for pde6α′ (red) and red opsin (green). Central (J) and peripheral (K) retinas. (L, M) Sections of 6 dpf photoreceptor layers labeled with fluorescent-conjugated RNA probes for pde6α′ (red) and rhodopsin (green). Central (L) and peripheral (M) retinas. In both peripheral and central retinas, the expression of red opsin mRNA overlaps with that of pde6α′, whereas the expression of rhodopsin mRNA does not overlap with that of pde6α′.