AIM: To use the tyrosinase minigene as a visual marker to perform microinjection training and improve the techniques related with transgene to greatly elevate the efficiency of gene transfer.METHODS: A mouse tyrosinase minigene, i.e., TyBS,in which the 2.25-kb authentic genomic 5' non-coding flanking sequence of mouse tyrosinase was fused to a mouse tyrosinase cDNA, was introduced into the fertilized eggs of outbred Kunming albino mice.RESULTS: Of the 11 animals that developed from the injected eggs, two mice (P1 and #8) exhibited pigmented hair (P1) and eyes (P1 and #8), as confirmed by PCR analysis for the tyrosinase minigene integrated into the genome. When founder P1 was bred to Kunming male mouse, six progeny out of 11 offspring inherited the transgene and the pigmented-eye phenotype.CONCLUSION: Taken together, these results suggest that this minigene encodes the active tyrosinase protein and that its 5' flanking region contains the sequences regulating the expression of mouse tyrosinase gene as expected. We have rescued the albino phenotype by introduction and expression of a functional tyrosinase minigene in the Kunming albino mouse and the transgene can be passed to subsequent generation.These findings also indicate that TyBS can be a useful visual marker gene in the co-transgenic experiments.