PHENOTYPIC RESCUE OF THE ALBINO MUTATION IN THE MEDAKAFISH (ORYZIAS-LATIPES) BY A MOUSE TYROSINASE TRANSGENE

Mutations of the tyrosinase gene are one common cause of a similar phe notype in all vertebrates, known as albinism. In an attempt to contrib ute to an understanding of the genetic hierarchy governing the develop ment of pigmentation, we have used a mouse tyrosinase minigene under t he control of its 5.2 kb upstream promoter region to rescue two differ ent albino mutations in the medakafish, Oryzias latipes. Around hatchi ng stages an almost perfect phenocopy of the wildtype pigmentation was obtained. Subsequent ectopic melanin overproduction indicated a possi ble incompatibility of the heterologous mouse promoter for stable expr ession during the entire ontogenesis. Like in some tyrosinase transgen ic mouse lines a strong variegation effect was observed. The transgene -mediated pigmentation phenotype was obtained up to the eighth offspri ng generation. The phenotypic effects of the tyrosinase transgene in d ifferent albino mutant strains places the i(3)-locus upstream and the b-locus downstream of the tyrosinase locus i(l) in the genetic hierarc hy leading to wildtype pigmentation. (C) 1997 Elsevier Science Ireland Ltd.