How Now Rat Clones From Cows? Bovine Eggs Used To Create Embryos Of Other Species
It sounds like a recipe for a witch’s brew: Scientists in Wisconsin have mixed ear of pig and egg of cow - also ear of rat and egg of cow and a variety of other crossspecies combinations - to clone living embryos of rats, pigs, sheep and monkeys.
The series of experiments, being described Monday at a meeting in Boston, represents a new and surprising twist on the cloning techniques that led to the birth of Dolly the sheep.
The work suggests that cow eggs, available by the thousands from slaughterhouses, contain all the ingredients and molecular machinery needed to grow embryos of many species. All that’s required is genetic material from the species to be cloned - taken from, say, a bit of an animal’s ear - mixed with a cow egg that’s had its own genes removed.
Natural chemicals in the cow egg can apparently activate the foreign species’ genes, and soon an embryo of that species is growing in a laboratory dish, ready to be transferred to a surrogate mother animal.
The work is shedding light on the cellular mechanisms that coordinate the earliest stages of embryo development. And eventually, researchers said, the technique may allow conservationists to save threatened species with just a scraping of cells from a rare animal’s skin and a batch of cow eggs.
“It’s potentially very useful for endangered species,” said Tanja Dominko, who led the work with Neal L. First, a pioneer cattle cloner, at the University of Wisconsin in Madison. “If you want to make a rhino, you just take an ear punch from the rhino,” which contains hundreds of skin cells, and fuse each of those cells to its own cow egg.
“I’m intrigued by this and by where this may go,” said Carl Pinkert, a developmental biologist at the University of Alabama in Birmingham. Like others, Pinkert expressed some surprise that the developmental machinery inside cow eggs is similar enough to those in other species to develop embryos in those species.
Scientists said they are intrigued by the idea of using cow eggs to help clone endangered species. Previous speculation about cloning such species had been tempered by the assumption that scientists would have to use egg cells from the species they wanted to clone. It is difficult to get egg cells without harming an animal. But if cow eggs could be used instead, a single endangered animal could provide enough cells to produce an entire clutch, herd, flock or swarm of individuals.
The plan isn’t perfect. Clones, which are genetically identical, could suffer from inbreeding. And each embryo would have to be implanted into a surrogate mother of the same species, of which there may be few.
xxxx Animal farm So far, the researchers have grown apparently healthy sheep, monkey, rat, pig and cow embryos from cow eggs. But none of the embryos have grown into mature animals, and it’s possible that the technique will never lead to live births.