FELINE AIDS RESEARCH
Glow cat: fluorescent green felines could help study of HIV
Scientists hope cloning technique that produced genetically modified cats will aid human and feline medical research
by Alok Jha / 11 September 2011
It is a rite of passage for any sufficiently advanced genetically modified animal: at some point scientists will insert a gene that makes you glow green. The latest addition to this ever-growing list – which includes fruit flies, mice, rabbits and pigs – is the domestic cat. US researcher Eric Poeschla has produced three glowing GM cats by using a virus to carry a gene, called green fluorescent protein (GFP), into the eggs from which the animals eventually grew. This method of genetic modification is simpler and more efficient than traditional cloning techniques, and results in fewer animals being needed in the process. The GFP gene, which has its origins in jellyfish, expresses proteins that fluoresce when illuminated with certain frequencies of light. Poeschla, of the Mayo Clinic in Rochester, Minnesota, reported his results in the journal Nature Methods. This function is regularly used by scientists to monitor the activity of individual genes or cells in a wide variety of animals. The development and refinement of the GFP technique earned its scientific pioneers the Nobel prize for chemistry in 2008.
In the case of the glowing cats, the scientists hope to use the GM animals in the study of HIV/Aids. “Cats are susceptible to feline immunodeficiency virus [FIV], a close relative of HIV, the cause of Aids,” said professors Helen Sang and Bruce Whitelaw of the Roslin Institute at the University of Edinburgh, where scientists cloned Dolly the sheep in 1996. “The application of the new technology suggested in this paper is to develop the use of genetically-modified cats for the study of FIV, providing valuable information for the study of Aids. “This is potentially valuable but the uses of genetically modified cats as models for human diseases are likely to be limited and only justified if other models – for example in more commonly used laboratory animals, like mice and rats – are not suitable.” Dr Robin Lovell-Badge, head of developmental genetics at the Medical Research Council’s national institute for medical research, said: “Cats are one of the few animal species that are normally susceptible to such viruses, and indeed they are subject to a pandemic, with symptoms as devastating to cats as they are to humans. “Understanding how to confer resistance is … of equal importance to cat health and human health.”
THAT GLOW GREEN
Glowing transgenic cats could boost AIDS research
by Andy Coghlan / 11 September 2011
Three cats genetically modified to resist feline immunodeficiency virus (FIV) have opened up new avenues for AIDS research. The research could also help veterinarians combat the virus, which kills millions of feral cats each year and also infects big cats, including lions. Prosaically named TgCat1, TgCat2 and TgCat3, the GM cats – now a year old – glow ghostly green under ultraviolet light because they have been given the green fluorescent protein (GFP) gene originating from jellyfish. The GM cats also carry an extra monkey gene, called TRIMCyp, which protects rhesus macaques from infection by feline immunodeficiency virus or FIV – responsible for cat AIDS. By giving the gene to the cats, the team hopes to offer the animals protection from FIV. Their study could help researchers develop and test similar approaches to protecting humans from infection with HIV.
Already, the researchers have demonstrated that lab cultures of white blood cells from the cats are protected from FIV, and they hope to give the virus to the cats to check whether they are immune to it. “The animals clearly have the protective gene expressed in all their tissues including the lymph nodes, thymus and spleen,” says Eric Poeschla of the Mayo Clinic College of Medicine in Rochester, Minnesota, who led the research. “That’s crucial because that’s where the disease really happens, and where you see destruction of T-cells targeted by HIV in humans.” The animals are not the first GM cats, but the new method is far more efficient and versatile than previous techniques. The first cloned cat, born in 2001, was the only one to survive from 200 embryos, each created by taking an ear cell from cats, removing the nucleus and fusing it with a cat egg cell emptied of its own nucleus. Poeschla’s technique is far more direct, far more efficient and far simpler, and has already been used successfully to make GM mice, pigs, cows and monkeys. He loads genes of interest into a lentivirus, which he then introduces directly into a cat oocyte, or egg cell. The oocyte loaded with the new genes is then fertilised and placed in the womb of a foster mother. From 22 implantations, Poeschla achieved 12 fetuses in five pregnancies, and three live births. And out of the 12 fetuses, 11 successfully incorporated the new genes, demonstrating how efficient the method is. One surviving male kitten, TgCat1, has already mated with three normal females, siring eight healthy kittens that all carry the implanted genes as well, showing that they are inheritable. But there are doubts about whether cats will replace monkeys as the staples of HIV research. “It’s fantastic they’ve created GM cats,” says Theodora Hatziioannou of the Aaron Diamond AIDS Research Center in New York City. “But what makes research in monkeys so much better is that SIV in monkeys is much more closely related to HIV, so it’s more straightforward to draw conclusions than it would be with FIV.
THAT GLOW RED
May 14, 2009 / Photo by Choi Byung-kil/Yonhap via AP
How does it glow?
Red fluorescent protein, introduced via a virus into cloned DNA, which was implanted in cat eggs, then implanted in mother (2007)
What can we learn?
Scientists at Gyoengsang National University in South Korea both cloned a Turkish Angora house cat and made it fluorescent—as shown in the glowing cat (left) photographed in a dark room under ultraviolet light. (The nonfluorescent cat, at right, appears green in these conditions.) The scientists weren’t the first to clone a cat–they weren’t even the first to clone a fluorescent cat. But they were the first to clone a cat that fluoresces red. It’s hoped that the red glow, which appears in every organ of the cats, will improve the study of genetic diseases.
email : Poeschla.Eric [at] mayo [dot] edu
Mayo Clinic Teams with Glowing Cats Against AIDS, Other Diseases
New Technique Gives Cats Protection Genes / September 11, 2011
Mayo Clinic researchers have developed a genome-based immunization strategy to fight feline AIDS and illuminate ways to combat human HIV/AIDS and other diseases. The goal is to create cats with intrinsic immunity to the feline AIDS virus. The findings — called fascinating and landmark by one reviewer — appear in the current online issue of Nature Methods. Feline immunodeficiency virus (FIV) causes AIDS in cats as the human immunodeficiency virus (HIV) does in people: by depleting the body’s infection-fighting T-cells. The feline and human versions of key proteins that potently defend mammals against virus invasion — termed restriction factors — are ineffective against FIV and HIV respectively. The Mayo team of physicians, virologists, veterinarians and gene therapy researchers, along with collaborators in Japan, sought to mimic the way evolution normally gives rise over vast time spans to protective protein versions. They devised a way to insert effective monkey versions of them into the cat genome. “One of the best things about this biomedical research is that it is aimed at benefiting both human and feline health,” says Eric Poeschla, M.D., Mayo molecular biologist and leader of the international study. “It can help cats as much as people.”
Dr. Poeschla treats patients with HIV and researches how the virus replicates. HIV/AIDS has killed over 30 million people and left countless children orphaned, with no effective vaccine on the horizon. Less well known is that millions of cats also suffer and die from FIV/AIDS each year. Since the project concerns ways introduced genes can protect species against viruses, the knowledge and technology it produces might eventually assist conservation of wild feline species, all 36 of which are endangered. The technique is called gamete-targeted lentiviral transgenesis — essentially, inserting genes into feline oocytes (eggs) before sperm fertilization. Succeeding with it for the first time in a carnivore, the team inserted a gene for a rhesus macaque restriction factor known to block cell infection by FIV, as well as a jellyfish gene for tracking purposes. The latter makes the offspring cats glow green.
The macaque restriction factor, TRIMCyp, blocks FIV by attacking and disabling the virus’s outer shield as it tries to invade a cell. The researchers know that works well in a culture dish and want to determine how it will work in vivo. This specific transgenesis (genome modification) approach will not be used directly for treating people with HIV or cats with FIV, but it will help medical and veterinary researchers understand how restriction factors can be used to advance gene therapy for AIDS caused by either virus. The method for inserting genes into the feline genome is highly efficient, so that virtually all offspring have the genes. And the defense proteins are made throughout the cat’s body. The cats with the protective genes are thriving and have produced kittens whose cells make the proteins, thus proving that the inserted genes remain active in successive generations.
The other researchers are Pimprapar Wongsrikeao, D.V.M., Ph.D.; Dyana Saenz, Ph.D.; and Tommy Rinkoski, all of Mayo Clinic; and Takeshige Otoi, Ph.D., of Yamaguchi University, Japan. The research was supported by Mayo Clinic and the Helen C. Levitt Foundation. Grants from the National Institutes of Health supported key prior technology developments in the laboratory.