Reported in this week's  Nature Methods, researchers at the Mayo Clinic created transgenic cats that possess a heightened immune system and a green, glowing hue.The scientists used the green fluorescent protein (GFP) gene, which has its origins in jellyfish, as a marker to visualize another gene of interest. The GFP gene expresses proteins that fluoresce when illuminated with the right kind of light and is regularly used in transgenic experiments to track gene activity.Along with the GFP gene, cats were bestowed with a protein called TRIMCyp. Found in humans and monkeys but not in cats, it prevents the animals from becoming infected with feline immunodeficiency virus (FIV), the feline version of human AIDS.Cat eggs containing both of these introduced genes were fertilized and injected into adult female cats. Three kittens were born that carried the new genes. When blood samples from the transgenic kittens were exposed to FIV, the virus did not replicate well, suggesting that the TRIMCyp protein provides some level of protection to the cats.Science News covers the story here, along with a great glowing cat photo.