The Tyrosinase Gene from Medakafish : Transgenic expression Rescues Albino Mutation

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We have determined the 9.8 kb genomic nucleotide sequence of the tyrosinase gene and its 5' upstream region from a telost, medakafish (Oryzias latipes), and shown thata the coding region is composed of five exons and four introns, spanning 4.7 kb. While the number and sizes of the exons were found to be similar to those of mammalian tyrosinase gens, however, the total size of the coding region (4.7kb) was demonstrated to be less thatn one tenth those of mouse (ca.70 kb) and human (>70 kb) genes. transgenic experiments were carried out by microinjecting two kinds of plasmic clones into fertilized eggs of the albino i^1 mutant ; one consisting of the genomic tyrosinase gene with the 10 kb 5' upstream region, and the other the tyrosinase cDNA with the 3 kb 5' upstream region. The results showed that 53 and 45 of 114 and 118 transgenic eggs, respectively, developed normally beyound hatching and 15 and 10 exhibited a mosaic pattern of pigmentation. Thus, transgenic expression rescued from the albino-i^1 mutation, and the i locus of the medaka genome can be concluded to encode the tyrosinase gene.