June 19, 2001 - BBC - Journal Genes and Development

Scientists in the United States have created a genetically modified mouse that changes color.

The pure white rodent grows a brown coat when a special supplement is added to its diet.

By studying the function of particular genes during development we can begin to understand how an alteration in the function might lead to human disease.

When the sugary substance is withdrawn, the mouse reverts to its white coat.

Researchers say the work could lead to a better understanding of human genetic diseases and cancer.

The study is bound to prove controversial among groups opposed to animal research.

Dr Heidi Scrable of the University of Virginia, Charlottesville, said: "It demonstrates that we can turn genes on and off in the mouse, which is the principal experimental animal that we have for modelling human diseases."

She said the mouse would be an important tool for medical research since some genes are virtually identical in the mouse and the human.

One particular challenge is cancer. The team plans to study a gene implicated in many cancers in a bid to find out how common tumours develop.

Dr Scrable told BBC News Online, "By studying the function of particular genes during development we can begin to understand how an alteration in that function might lead to human disease."

Pink eyes, brown eyes

The team used genetic engineering and natural breeding to alter the genes of an albino strain of mouse.

The rodents lack pigment in the eyes, skin, and fur because of a genetic mutation so they have pink eyes and a pure white coat.

The neuroscientists added two extra genes to the mice - one of them a normal mammalian pigment-producing gene.

The other gene, derived from a bacterium, is a regulator that switches the pigment gene on and off in response to a dietary trigger.

The scientists ended up with mice that can change their coat colour and even the colour of their eyes.

Adding a sugar-like substance to an animal's drinking water switches on the gene that makes the pigment melanin.

The mouse then grows a brown coat and its pink eyes become dark. On removing the sugar, the albino coat grows back, but the animal's eyes stay black because the pigment does not break down.

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