Faithful expression of living color reporter genes in transgenic medaka under two tissue-specific zebrafish promoters.

To test tissue specificity of zebrafish gene promoters in a heterologous fish species, two transgenic medaka lines under two zebrafish promoters were generated. Under the zebrafish skeletal muscle-specific mylz2 promoter, transgenic medaka expressed green fluorescent protein (GFP) exclusively in skeletal muscles, mimicking the endogenous medaka mylz2 mRNA expression and also identical to GFP expression in mylz2:gfp transgenic zebrafish. A madaka mylz2 promoter was also capable of directing skeletal muscle-specific GFP expression in transient transgenic zebrafish embryos. In the krt8:rfp transgenic medaka line with the zebrafish epithelial krt8 promoter, red fluorescent protein was specifically expressed in the skin epithelia as well as the epithelial lining cells of the anterior digestive tract, which was also identical to GFP expression in krt8:gfp transgenic zebrafish. Therefore, the two zebrafish promoters faithfully function in a heterologous fish species, and it is likely that the mechanisms of tissue-specific expression are largely conserved among fish species.