New Techniques Make Cloning Genetically-altered Animals
New Scientist 16 Aug 97
'To date, 80 per cent of the pregnancies have passed the 90-day stage'
HERDS of cloned farm animals could be a common sight within a few years, following a breakthrough by the American company ABS Global of De Forest, Wisconsin. The company has developed a technique for mass-producing clones. Last week, it showed off its first success, a six-month-old calf called Gene. Gene was created from a cell removed from a fetal calf. But the process works just as well with the cells of adults, says Michael Bishop, ABS's director of research. This is important because it allows the cloning of animals that have proved their worth. More than 10 clones of adult cattle have been implanted in cows and are due to be born over the next few months. Earlier this year, Scottish researchers revealed that they had cloned Dolly from the cell of an adult sheep (This Week, 1 March, p 4). To make their clone, the ABS team took .a cell from the donor animal and fused it with an unfertilised egg that had its nucleus removed. The egg developed into an embryo with the same genes as the donor cell. The team then divided the embryo into individual cells and grew these into new embryos before implanting them in surrogate mothers. Although ABS won't release details of its new process pending patents, Bishop says the key breakthrough was establishing a "genetically stable" cell line to serve as the basic stock for cloning. In 1994, Neal First of the University of Wisconsin in Madison cloned cows using the cells of a developing embryo. But there is a limit to how many clones can be produced this way. When the team at the university cultured more than a few thousand copies, the cells began to accumulate genetic flaws. ABS says it has found a way to prevent or repair those flaws. "These cells can be used to make unlimited numbers of exact duplicates'of the animal that they are derived from," says Bishop. Bishop also claims a high success rate. Half the embryos implanted in surrogate mothers resulted in pregnancies. To date, 80 per cent of the pregnancies have passed the critical 90-day milestone in the cows' 1 0-month gestation, after which the chance of miscarriage drops significantly. By contrast, Dolly was the only success out of 277 implanted embryos. Marc van't Noordende, chief executive of ABS Global, says the technology has enormous potential for the cattle-breeding industry. Cloning would enable cattle and dairy producers to maximise the benefits of desirable traits, such as high milk production or tender meat. The new process could also speed the development of genetically engineered cows-for example, those that produce pharmaceuticals in their milk. Techniques for adding new genes to an animal's chromosomes have a success rate of one cell in a thousand. Performing it on millions of clonable cells at once, says First, could vastly increase the number of successes. Daniel Pendick, Milwaukee
BOSTON Jan 98 United States researchers say they have created a small herd of cloned calves a step in the eventual commercial production of animals for human therapy as well as noulishment. The scientists, Dr Jaxnes Robl and Dr Steven Stice . of the University of Massachusetts at Amherst, said three calves all males -were bom last week at a Texas ranch operated by Ultimate Genetics. Mve more calves were on the way. Dr Robl said his technique was a significant advance on the method developed by PPL Therapeutics and Scotland's Roslin Institute to make Dolly, the cloned sheep whose birth was announced last year and Polly, a clone who also carries human genes. 'Cow cloning is more significant from a conunercial standpoint and we've also developed a simpler procedure than that used in the sheep," said Dr Robl. That the three Holsteins already bom and the rest expected to be delivered before the end of the month are all males "was luck," Dr Robl said. . "We were trying to prove a principle," Dr Stice said. "it will be easy to produce females." Their technique involves. taking eggs from slaughtered cows, inserting genetically-altered cell nuclei containing a "marker" gene and culturing the eggs. Those eggs are then shipped to the Franklin, Texas, ranch where they are "implanted in just regular, ordinary cows," Dr Robl said. The calves produced so far do not contain a therapeutic gene - one that does something. The marker gene just lets scientists know the hit-and-miss technique of tinkering with the animal's genes did indeed work. The technique should shave a two years off the time necessary to begin producing milk containing proteins used to treat a variety of human ailments, Dr. Robl said. Under a five-year $US10 million contract with Genzyme Transgenics, Dr Robl and Dr Stice's Worcester, Massachusetts-based Advanced Cefl Technology is to produce genetically identical cattle they hope will produce milk containing human serum albumin protein. Human serum albumin is used to maintain fluid balance and is regularly given to patients who have lost a lot of blood. Currently made from pooled human plasma, about 440 tonnes of plasma-derived albumin are used throughout the world each year with sales of about $USI.5 billion. The researchers expect an individual cloned transgenic dairy cow could produce about 80 kgs of human albumin annually. They have also finished preliminary Nwork on developing dopamine cells in cows and transplanting them into rats bred to develop Parkinson's disease. Parkinson's is the second most common neurodegenerative disorder after Alzheimer's disease., It afflicts about 1 per cent of people over the age of 50. Dr Robl and Dr Stice declined to discuss their progress in that area, saying they wanted their work to be published in a scientific journal first.
Cloned Clones Sci Am Oct 98 14
This time the creators of Dolly the cloned sheep have truly been outdone. An international team of scientists led by Ryuzo Yanagimachi of the University of Hawaii has created multiple clones and clones of those clones using a new technique. A paper describing the success appeared in the journal Noture on July 23. The group is the first to duplicate mammals in a reproducible fashion, making more than 50 mice that genetically match their sister/parent, sister/grandparent and sister/great-grandparent. Some of the animals now reside at the Liberty Science Center in Jersey City, N.J. For more information, see http://www. sciam.com/explorations/I 998/ 072798clone/index.htmi at the ScientificAmerican Web site.