University designs green mice that glow in the dark

Biologists at Osaka University have created genetically-altered mice that glow green in the dark and claimed June 11 that they have bred “the world’s first light-emitting mammals.”

Assistant Professor Masaru Okabe and his team at the Osaka University Microbiology Laboratory said they used the latest technology to inject DNA from light-emitting jellyfish into the fertilized eggs of mice. The DNA is taken from a special protein, called GFP, in the jellyfish. Like the jellyfish, the mice emit green light, produced from the GFP reproduced in cells throughout the bodies of the mice, they said.

“We have found that this characteristic is passed down to offspring,” Okabe said. “The result can be used as a ‘marker’ technology in which only certain cells are made to glow for medical research.”

The experiment, according to Okabe, shows the method can be used to develop humane ways of conducting animal experiments. Genetic engineering can be used to determine the effects of new cancer drugs by devising a way so that only the cancer cells glow. This means killing the animals after experiments to determine the effects of the drugs will no longer be necessary, he said.

In the past, flies and fish have been genetically altered to contain GFP, but the latest experiment is the first successful one for mammals, Okabe said. Many attempts to make the “florescent mice” failed until the researchers found a certain vector, or virus, to incorporate the jellyfish DNA into the DNA of the mice, he said.

The mice no longer appear to be green when they become adults because hair covers their bodies, but their feet and the area around their mouths, where hair is thin, would still glow, Okabe said. The blood of the mice is still red, but the white blood corpuscles, when separated, are green, he said.