Expression of the tyrosinase-encoding gene in a colorless melanophore mutant of the medaka fish, Oryzias latipes.
In the medaka fish Oryzias latipes many mutants for body colors have been isolated. Among them, a colorless melanophore mutant b, carrying b alleles homozygously, has pigmented black eyes but orange-colored skin with amelanotic melanophores, suggesting the presence of a tissue-specific mechanism of melanin formation. To cast light on the molecular basis of the mechanism, we have cloned cDNAs for tyrosinase (Tyr), a key enzyme in melanin biosynthesis, from the wild-type (wt) fish. DNA sequence analysis revealed that all clones encode a protein of 540 amino acids, having five potential glycosylation sites and two copper-binding sites that are characteristic features of Tyr. Genomic DNA blot analysis disclosed that the Tyr gene is present as a single copy in the fish genome. Using a cDNA clone as a probe, RNA blot analysis was carried out. In the wt, the 2.2-kb Tyr mRNA was expressed in eyes and skin but not in liver, corresponding to tissue-specific melanin formation. In the b mutant, contrary to expectation, the mRNA was detected not only in eyes but also in amelanotic skin. Therefore, pigmentation of the skin controlled by b is not directly related to expression of the Tyr gene.
Inagaki
H
H
Department of Biology, Faculty of Science, Nagoya University, Japan.
Bessho
Y
Y
Koga
A
A
Hori
H
H
D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D017931:DNA Primers; D006720:Homozygote; D015151:Immunoblotting; D008099:Liver / Q000201:enzymology; D008547:Melanophores / Q000201:enzymology*; D008969:Molecular Sequence Data; D014442:Monophenol Monooxygenase / Q000096:biosynthesis* / Q000235:genetics; D009154:Mutation; D009990:Oryzias / Q000235:genetics*; D016133:Polymerase Chain Reaction; D015183:Restriction Mapping; D012880:Skin Pigmentation / Q000235:genetics*
D017931:DNA Primers; D014442:Monophenol Monooxygenase