TOKYO - Japanese scientists have created what they say are the world's first fluorescent mammals: mice that glow in the dark in the interest of science.
Geneticists at Osaka University bred the mice by injecting embryos with the DNA of a species of North American jellyfish that glows under light. When the mice are viewed under ultraviolet light, their bodies appear a gleaming green.
Professor Masaru Okabe and his team started the project four years ago in an effort to develop new methods to observe the internal development of fetuses.
Okabe says medical researchers will be able to use the technique in a variety of ways, including tracing white blood cells in cancer research.
"We have also developed the technology to make specific cells glow as markers, so the effects of research can be observed without killing the animals and opening them up," said Dr. Shuichi Yamada, a team member.
A scientist not involved in the project questioned what this means for science, predicting that researchers will still have to cut up test mice to examine the full effects of any experiments.
"The marker technology has potential. But I have my doubts as to how significant a breakthrough it is for medical research," said Robert Shiurba, a biologist at Tokyo University. "They should have made the announcement on Halloween."
The vibrant hues of the experimental mice disappear when hair grows over their bodies, but their feet and mouths continue to glow well into adulthood.
"The technique can be applied to other mammals, and since they are injected at the fertilized-egg stage the effects will be transmitted to offspring," Yamada said.
The researchers believe the technology could "open the door to a more humane approach to medical research."
Biologists often cut open test animals to study what happens when they are injected with drugs or diseases. Now they could peer into the innards of the glowing baby rodents to trace the growth and progress of cells.
The mice glow strictly for science, Yamada said. Researchers have no intention of marketing them as novelty pets.