First there were glow-in-the-dark fish, then rats, rabbits, insects, even pigs. And, now, researchers have inserted the jellyfish genes that make fluorescent proteins into Felis catus, or the common household cat.

The goal was just to make sure that the researchers could successfully insert novel genes into the cats. Past efforts at cloning and injecting DNA into fertilized cat embryos, among other genetic modification techniques, had failed. But the good doctors at the Mayo Clinic and Yamaguchi University in Japan succeeded by injecting a lentivirus bearing the novel genetics directly into unfertilized cat eggs. (Human immunodeficiency viruses 1 and 2 (HIV-1 and HIV-2), feline immunodeficiency virus (FIV) and simian immunodeficiency virus (SIV) are all lentiviruses, named for their slow incubation period.)

The result is visible to the naked eye (under blue light).

The goal is to use genetically modified cats as a better proxy for human diseases. After all, FIV plagues cats in much the same way that HIV plagues people. For that reason, cats can serve as useful animal models for learning more about the human version of the disease. The researchers, or their colleagues, plan to continue manipulating the cat genome to test potential gene therapies for HIV and other potential cures for AIDS.

But it's also only a matter of time until a night-glowing cat (say goodbye to nightlights and tripping over the cat!) becomes a breed and joins the GloFish at the pet store.

Images: © Mayo Clinic