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Friday, 14 January, 2000, 05:25 GMT
Scientists 'clone' monkey
Not produced by the Dolly technique, but a clone nonetheless
Tetra may help research into human diseases
By BBC News Online Science Editor Dr David Whitehouse

Tetra is a rhesus monkey and the first primate to be "cloned" using a method that splits the original cells in an embryo to make multiple identical animals.

It is a technique that could produce genetically-identical animals for use in studies of human diseases like diabetes and Parkinson's.

The method is used often in cattle. A sperm and an egg are combined and the resulting embryo allowed to split into two cells, then four, then eight.

At the eight-cell stage, the embryo itself can be split to produce four genetically-identical two-cell embryos.

This is the first time the technique has proved successful in monkeys.

"This is just artificial twinning," said Professor Gerald Schatten, from the Oregon Regional Primate Research Center in Beaverton, US.

Dolly technique

In the Oregon research, it was hoped that each of the separated embryos would develop to the stage where they could be transferred to a surrogate mother for a "normal" pregnancy.
Splitting the embryo
Splitting the embryo
But not all the split embryos survived - only two were implanted in surrogates.

And only one had a normal pregnancy - Tetra was born 157 days later.

Although a limited number of clones can be produced this way, it is very different from the technique used to produce Dolly the sheep, the first cloned mammal and the subsequent clones of cattle, mice and goats.

Producing Dolly involved the transfer of the genetic material of an adult into an empty cell sack, something that could in principle produce as many clones as required.

The embryo splitting technique has pros and cons.

Because the cloning takes place after the formation of an embryo, the exact characteristics of the animal that will develop from the embryo are uncertain and will be exact copies only of themselves.

Only if embryos are produced using the Dolly technique will the animals be genetically identical to another single (adult) individual.

Human ailments

The motivation of the researchers, who report their work in the journal Science, is to produce genetically-invariable subjects for the study of human diseases.

At the moment, monkeys are used in the study of human ailments, but the genetic variation of groups of monkeys can make the evaluation of their responses to procedures and medicines very difficult.

Having a batch of genetically-identical monkeys would simplify things and would make interpreting results much more straightforward.

"In order to move discoveries from the laboratory bench to a patient's bedside, we need to have genetically-identical animals that would provide the information needed before these new therapies are tested on people," said Professor Schatten.

"Our contribution is to help provide the genetically-identical models in which lifesaving cures can be perfected."

Stem cells

The method Professor Schatten's team used is not yet very efficient. The researchers made 368 embryos by splitting 107 embryos into two or four pieces. Tetra was the only success.

The team now has four other pregnant monkeys which, if their babies make it, are due to start delivering in May. The researchers plan to call two of the genetically-identical twins Romulus and Rhesus.

Professor Schatten also intends to freeze split embryos.

These could later be harvested for stem cells, the so-called master cells that can develop into any kind of cell in the body, and which scientists hope one day to use as tissue transplants to treat diseases such as diabetes and Parkinson's.

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See also:

24 Jun 99 | Sci/Tech
Cloning - where will it end?
24 Dec 99 | Sci/Tech
Clone hope to save panda
18 Jun 99 | Sci/Tech
First cloned human embryo revealed
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