Diana the sheep and Cupid the sheep have human genes
by Tamara Traubman
The Scottish scientists who created Dolly the cloned sheep will announce today that they have achieved a breakthrough in genetic engineering. Using a method similar to Dolly's cloning method, they created two sheep carrying human genes in each of their body cells.
Experts said that this was a "tremendous breakthrough" and one of the "resounding" achievements of the year. Animals with human genes could be used to produce proteins and hormones to treat diseases. Theoretically, it will be possible to insert genes that cause diseases in humans and try new treatments on them, before trying them on humans.
Although additional development work will be required, animals inserted with human genes could be used as a "factory" for the production of organs for transplantation, including skin and internal organs. The integration of the genetic load of the patient needing a transplant into the organ of the animal that will be transplanted into him will reduce his body's rejection reaction to the transplant.
The technology that enabled the production of the two sheep, Diana and Cupid, is "a very significant breakthrough compared to other genetic engineering technologies," said Prof. Moshe Shani, a researcher at the Vulcani Institute. "Although it won't happen tomorrow or the day after tomorrow, but in principle, now everything is open. You can replace any gene of the animal with a gene of another animal, and be sure that it will integrate into the DNA of the animal and perform its function - for example, to produce a growth hormone or disrupt in a unique way genes whose activity is disastrous, such as the one that causes mad cow disease."
Until now, scientists who wanted to carry out genetic engineering in farm animals had only one method, limited and ineffective, in which they had no control over the location of the transplanted gene in the animal's DNA. Until the desired result was reached, the scientists had to implant genes in hundreds and thousands of fertilized eggs. "The existing method therefore required using an unrealistic number of eggs to get one animal that would produce the protein at the required level," said Prof. Shani, who is developing a method for transplanting human genes into goats.
The Scottish researchers - headed by Dr. Alexander Kind from the "PPL Therapeutics" company - took cells from a sheep and inserted into them a human gene responsible for the production of the alpha 1 antitrypsin enzyme. In patients with hereditary emphysema, this gene is defective, so their body does not produce the enzyme. They implanted another gene that served as a marker that showed them in which cells the gene reached its correct location - and used only those.
In the second stage, the scientists repeated the technology used to clone Dolly: they removed the nucleus from the cell containing the human genes (DNA is concentrated in the cell nucleus) and inserted it into an egg whose nucleus had been removed. Then - in a way that has not yet been explained since Dolly's replication - the egg continued to develop, as if it were a normal embryo that developed from an egg fertilized by a sperm.
The two lambs born carry the human gene in each of their body cells, and they produce the human enzyme that this gene dictates.
"Despite repeated attempts in animals, scientists have so far been able to direct a gene to its exact location only in mice. "Scientists have almost lost hope that they will ever be able to do this in other mammals," said Dr. Alan Bradley, from the Ord Hughes Institute, who wrote a commentary article accompanying the study published today in the scientific journal "Nature" We are undoubtedly now at the dawn of a new era in technology for genetic manipulation of mammals".
{Appeared in Haaretz newspaper, 29/6/2000{
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