Scientists have genetically modified cats by infecting their eggs with a virus containing a foreign gene first time this method has worked in a carnivore. Experts say the advance could make the cat a valuable new genetic model and potentially protect against an HIV-like
virusThere are two AIDS epidemics in the world :. One in humans, other cats. While we can be infected with HIV (HIV), cats are victims of feline immunodeficiency virus (FIV), which causes almost identical symptoms. The virus, known as lentiviruses, are sufficiently different that cats can not get HIV and people can not get FIV, but most of their basic biochemistry is the same.
Previous studies have suggested that a protein called TRIMCyp is what keeps humans and monkeys from being infected with FIV. The protein, which lack cats, is thought to recognize outer shell of the virus and the target to deteriorate.
Eric Poeschla, a molecular virologist at the Mayo Clinic in Rochester, Minnesota, wanted to know if the cats of TRIMCyp gene would be immune to FIV. But the only proven way to get a new gene into a cat, transfer of somatic cell nuclei, is tricky. The technique, which produced the famous sheep Dolly, involves replacing the nucleus of an egg cell with a nucleus of an adult cell that contains new genes and implantation of the egg in a female. The strategy works in only a fraction of cases. In cats, it has been used to create glowing kittens without other traits, just proof that it can be made to work.
Poeschla and colleagues turned to another method using a virus to carry genes into an egg cell that had worked in animals, including mice and cows, but never succeeded in a carnivore . Because the cells are easily infected by lentiviruses, researchers made a lentivirus containing TRIMCyp gene and a gene encoding a fluorescent protein. This allowed them to easily visualize the cells contained the new genetic material-chats with the green glow of the gene (see photo). After allowing the virus to infect eggs, the team fertilized with normal sperm cat and inject them into the fallopian tubes of 22 female cats. Each cat received 30-50 eggs.
Five cats became pregnant, with 11 embryos them, the team announced today online Nature Methods . Ten embryos contained the new genes, and five resulted in kittens, three of whom are still alive. (A kitten was stillborn and another died during childbirth.) The 23% success rate is much higher than the typical 3% seen with nuclear transfer of somatic cells, Poeschla said. In addition to a large number of animals by pregnancy, the number of transgenic animals by embryo is also high. "A big advantage is efficiency. Almost all of the offspring are transgenic [carry the new gene], so you're not screening hundreds of animals to find those transgenic. "
The effectiveness of the method is that half of the story, however. When the researchers tried to infect blood cells from genetically modified kittens with FIV, the virus does not replicate well. Poeschla and his colleagues next plan to test whether cats are resistant IVF, or, otherwise, if they are less likely to develop feline AIDS after infection.
researchers can use the same method to check whether other antiviral proteins of humans and apes affect transmission of FIV, says veterinarian Susan Vandewoude of Colorado State University in Fort Collins. the advance also makes it easier to use the cats as model organisms for other biological questions, she said. for example, visual cortex of the brain of a cat is a better model for humans than the visual cortex of the mouse. With an easier way to change the genes related to vision, researchers might be able to acquire an even greater understanding of how this part of the brain.
"I think the cats are easier to use as a model organism Now you can manipulate the genome," said Vandewoude. "They will not replace the mouse, but it gives another tool for scientists."
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