Word: jaenisch
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...himself. Last year, Yamanaka was the first to announce success with this approach, by exposing the cells to four growth factors and nutrients. But the stem cells he generated were genetically abnormal and unstable. Building on the initial technique, Yamanaka's group, as well as those led by Rudolph Jaenisch at Whitehead and Konrad Hochedlinger at HSCI, showed that the process does indeed work-and can generate stable stem cells that go on to develop into eggs and sperm that can produce healthy mice. "It's very exciting and we look forward to all there is to do from here...
...like taking all the words in a novel, jumbling them up and then trying to re-create the original book, putting sentences, pages and chapters back in the right order. The chances of that happening with 100% accuracy are minuscule, which helps explain why cloning is so inefficient. Rudolf Jaenisch, a geneticist at the Massachusetts Institute of Technology, estimates that 4% to 5% of the genes in a cloned animal's genome are expressed incorrectly--probably because of faulty methylation. "If you reprogram, it affects the whole genome," he says. "From what we know, I would argue that cloned animals...
...fact that clones have defects--however minor--only bolsters the arguments that scientists have made against human cloning. Based on his studies of the faults introduced by reprogramming, Jaenisch, for one, thinks human cloning is now out of the question. "I think we cannot make human reproductive cloning safe," he says. "And it's not a technological issue. It's a biological barrier. The pattern of methylation of a normal embryo cannot be re-created consistently in cloning...
...Jaenisch and Wilmut both see a role for cloning in treating human diseases--and perhaps someday conquering some of man's most intractable conditions. Wilmut and others have already created cow, sheep and pig cells genetically engineered to produce a particularly beneficial human protein, then cloned those cells to generate live animals able to make copious amounts of the target protein in their milk. It may be another 10 years or more before that approach yields anything safe and reliable enough to be used in real patients, and there is no guarantee that it will ever be successful...
...cell blossoms into a complex organism like a mouse or a human being. Someday the new technology could yield treatments for diseases such as cancer, thalassemia and sickle-cell anemia. In short, an increasing number of biologists and geneticists agree, the field of transgenic mice is hot. Says Rudolf Jaenisch, a molecular biologist with the Whitehead Institute for Biomedical Research in Cambridge, Mass.: "Everybody wants to jump on the bandwagon because it's such an interesting wagon to ride...