Cats that can glow in the dark from a new genetic engineering technique are helping scientists study molecules that could stop AIDS, researchers announced today (Sept. 11). So far, the researchers have created three genetically engineered kittens that can glow green and pass this gene onto their offspring. They explained that cats are much better models for AIDS viruses than are mice and other animals. In addition to opening a window into the virus in humans, the cat research may end up helping the felines themselves, the researchers said. Devastating AIDS pandemics The world is currently facing two devastating AIDS pandemics— one in humans, the other in domestic cats. The viruses responsible, human immunodeficiency virus (HIV) and feline immunodeficiency virus (FIV), are highly similar. “FIV causes AIDS with loss of infection-fighting T cells like HIV does in people, and cats get sick from virtually the same AIDS-defining opportunistic infections as humans who have untreated HIV,” said researcher Eric Poeschla, a molecular biologist and infectious disease specialist at the Mayo Clinic College of Medicine in Rochester, Minn. As such, researchers have long wanted to genetically experiment with cats to better understand how to combat AIDS. To create genetically modified animals, scientists insert genes into their genomes, often using benign viruses as the delivery vehicles. Investigators commonly target the earliest possible stages in an animal's development so the gene gets installed into all of its cells — any later, and the gene can end up in some tissues but not others. Tinkering with cat genes At first scientists created genetically engineered cats using cloning, which meant injecting a gene into one cell — from the skin, for instance — and then implanting the modified nucleus of that cell into an egg cell that had its nucleus removed; the resulting cell then develops into an embryo much like a fertilized egg would. In this manner, researchers generated felines that were either fluorescent red or green, a glow-in-the-dark cat being visible proof of the genetic engineering succeeding. However, this kind of cloning is very difficult to perform, as it essentially involves delicate surgery on cells. In addition, the manhandling that both nucleus and egg experience and the “reprogramming” the nucleus undergoes from adult to embryonic status often leads to animals that might look normal but can have aberrations on the molecular and cellular level. Now scientists have developed a new way to create genetically engineered domestic cats where they modify egg cells directly with viruses. The amount of genetic material they implanted within the cats was tiny — if the entire string of DNA that is the cat genome were unraveled and depicted as a highway reaching across the United States from New York to Los Angeles, the inserted material would be equal in length to one of the dashed yellow lines in the middle of the highway somewhere out in Nebraska, Poeschla said. This efficient process, the first time sex cells of a carnivore have been genetically modified, led to embryos that robustly expressed the implanted gene without all the complexities cloning can involve. The result — three healthy kittens that glowed green when a blue light was shone on them and transmitted the gene to their offspring. The researchers then applied this approach to investigating resistance to AIDS. “We want to see if we can protect the domestic cat against its AIDS virus, if we can protect any species, eventually including ours, against its own AIDS virus,” Poeschla told LiveScience. The aim of future treatments is a gene therapy that can introduce protective genes into people that help them fight off HIV, he added. To do so, they created transgenic cats that generated or expressed antiviral proteins taken from rhesus monkeys. Such molecules can block retroviruses such as HIV and FIV.Preliminary results suggested cells from these cats grown in the lab resisted replication of the feline AIDS virus FIV, keeping it from spreading. “We haven't shown cats that are AIDS-proof,” Poeschla cautioned. “We still have to do infection studies involving whole cats. That the protection gene is expressed in the cat lymphoid organs, where AIDS virus spread and cell death mostly play out, is encouraging to us, however.” Millions of cats dying The researchers stress their work could also help cats themselves, not just humans. Since FIV afflicts feral cats the most, the virus causes a lot of unwitnessed, unattended and unrelieved feline suffering, with millions of cats dying annually worldwide from AIDS, often painfully and alone. “Millions more suffer with chronic illness from the virus,” Poeschla added. “Supporting this research can help cats as much as people.” Although this research on transgenic cats has so far concentrated on AIDS, there are many other diseases that cats and humans share that genetically modified felines could help shed light on in a way that mice and other experimental animals cannot. “Some feline organs, such as the eye, are much more similar to humans than the same organs in mice,” Poeschla explained. “The cat brain, particularly the cerebral cortex and vision-processing parts, is the best understood of any species.” As such, transgenic cats “might be of help in understanding the workings of the brain and neurological diseases such as Alzheimer's, or with genetic illnesses and major eye diseases such as glaucoma or macular degeneration,” he added. The scientists detailed their findings online in the journal Nature Methods. Follow LiveScience for the latest in science news and discoveries on Twitter @livescience and on Facebook.
Everyone knows that cats can see in the dark, but that wasn’t good enough for some New Orleans scientists. They produced Mr. Green Genes, a cat that glows in the dark and is destined to be more than just a novelty for Halloween parties. He’s a nearly 6-month-old orange tabby but, under ultraviolet light, his eyes, gums and tongue glow a vivid lime green, the result of a genetic experiment at the Audubon Center for Research of Endangered Species. Mr. Green Genes is the first fluorescent cat in the United States, said Betsy Dresser, the center’s director. The researchers made him so they could learn whether a gene could be introduced harmlessly into the feline’s genetic sequence to create what is formally known as a transgenic cat. If so, it would be the first step in a process that could lead to the development of ways to combat diseases via gene therapy. The gene, which was added to Mr. Green Genes’ DNA when he was created earlier this year in the Audubon center’s laboratory, has no effect on his health, Dresser said. Cats are ideal for this project because their genetic makeup is similar to that of humans, said Dr. Martha Gomez, a veterinarian and staff scientist at the center. To show that the gene went where it was supposed to go, the researchers settled on one that would glow. The gene “is just a marker,” said Leslie Lyons, an assistant professor of population health and reproduction at the School of Veterinary Medicine at the University of California, Davis, who is familiar with the Audubon center’s work. “The glowing part is the fun part,” she said. — Nobel feat — Glowing creatures made international news earlier this month when the Nobel Prize in Chemistry was awarded to three scientists who had discovered the gene through their work with jellyfish. They used the gene, whose formal name is enhanced green fluorescence protein, to see how things work inside animals and even inside cells. Mr. Green Genes — his name comes from Mr. Green Jeans, a character on the long-departed “Captain Kangaroo” television show — is deeply suspicious of strangers. He spends most of his days napping, and he doesn’t like being held when he doesn’t want to be cuddled. In normal light, the 7-pound cat, who lives at the center, looks and acts like any other feline. But turn out the room lights and switch on some black light, and you can see glowing ears, nostrils, eyes and gums. Those body parts light up because the protein is more likely to express itself in mucous membranes, Lyons said. “You can’t lose that cat at night,” said C. Earle Pope, the center’s senior scientist. In theory, his litter box could glow, too, because cat droppings include epithelial cells, where the gene can be found. But there is entirely too much other stuff around them to allow for readily visible glowing without messy lab work, Gomez said. — ‘The frozen zoo’ — The Audubon center, which hugs the Mississippi River levee on Algiers’ Lower Coast, started its animal-cloning experiments in 2001. Two years later, Ditteaux, an African wildcat, was born there. He was the world’s first cloned wild carnivore. Cloning starts with cells — generally skin cells, Gomez said, because retrieval isn’t too invasive — and the cells’ genetic material is stored in a tank of liquid nitrogen where the temperature is 316 degrees below zero. The Audubon center has 12 such tanks of genetic specimens awaiting use; Dresser calls them “the frozen zoo.” For work with felines, eggs are collected from a donor cat — usually a domestic cat — and the DNA is removed and replaced. To create Mr. Green Genes, the fresh DNA included the fluorescent gene. Then the fertilized egg is inserted into a surrogate mother cat for a pregnancy lasting 65 to 70 days. After Ditteaux’s arrival, Gomez was invited to discuss it before a group of gene-therapy specialists, who, she said, were interested in the prospect of creating a genetic model for fighting diseases. The Audubon scientists want to use their technique to develop a gene-therapy treatment for cystic fibrosis, an incurable hereditary disease for which, Gomez said, there are no gene-therapy models. The fluorescence gene will go alongside the cystic-fibrosis gene and make it easy to spot. The long-term goal of this process, for which there is no timetable, is the production of what Gomez calls a “knockout gene.” Work on this project is under way, she said. “We are getting some preliminary data, but we don’t have the full funds for it.” — ‘He is my baby’ — Mr. Green Genes’ next role for the center will combine science and sex. He will become a stud so the Audubon team can determine whether the fluorescence gene can be transmitted. That should take no more than two breeding cycles, Gomez said. “If he is fertile and if the female is fertile, it should be quick,” she said. “The idea is not to have a lot of green cats around, but to demonstrate that the gene can be passed.” After that, he will retire to Gomez’s home, where two cats already live. “I feel that he is my baby,” said Gomez, who led the team that created him. “You have to realize that this is our first transgenic cat,” she said. “I don’t want him to go to just anybody. I feel he is mine.” . . . . . . . John Pope can be reached at [email protected] or 504.826.3317.