A transgene and its expression profile are stably transmitted to offspring in transgenic medaka generated by the particle gun method.

A particle gun is used in a potential method for introducing foreign genes into fish. In this paper, we report on the stable transmission of a transgene and its expression profile of the F4 generation in the transgenic medaka (Oryzias latipes). We established four transgenic strains, which contained a green fluorescent protein (GFP) gene controlled by a medaka beta-actin promoter, using a particle gun. One more transgenic strain was also generated by microinjection for comparison. In all five strains, the founder was discovered to be mosaic for the transgene. However, from the F1 to F4 generations, transgenes and their expression profiles were stably inherited in the Mendelian manner. The expression profile was common among the five strains regardless of the method for gene transfer: GFP fluorescence became detectable at an early neurula stage. In this stage, the fluorescence was observed ubiquitously in most tissues. As somite developed, GFP fluorescence became intense only in the skeletal muscle and lens but it decreased in other tissues. In adult fish, an intense fluorescence was restricted in the skeletal muscle and lens, while a considerably weak fluorescence was observed in the brain, gill, heart, kidney, spleen, and ovary. From these results, it was concluded that the transgene and its expression profile were stably transmitted to offspring, and thus the particle gun is an effective method for transgenesis in spite of its easiness.