French researchers succeeded in cloning rabbits; It is hoped that they will help in the study of human diseases
You are Tamara Traubman
To the growing list of species that scientists have succeeded in cloning, the rabbits are now added. A team of researchers from France will announce today that after three years of attempts, they succeeded in breeding rabbits. The rabbits will join the small beaver of cloned animals, which already includes sheep, cows, goats, mice, pigs, a cat, and two species of animals that are in danger of extinction.
The cloning of the rabbits is an achievement for scientists, who want to carry out experiments on them - among them, using them as "factories" for proteins with medical properties, which will be produced from their milk. In the past they succeeded in cloning a strain of mice, which are used as laboratory animals. However, the head of the research team, Dr. Jean-Paul Renard, says that there are experiments that are easier to do with rabbits. According to him, "they are bigger, and their body structure is more similar to that of humans."
Experiments on rabbits have already provided researchers with a lot of knowledge, especially in the study of heart and reproductive diseases. In addition, Renard says, their immune system is quite similar to that of humans, and they are useful in studying the mechanism that causes rejection of transplanted organs.
According to Renard, cloning will increase research possibilities. For example, it will be possible to develop medicines, with the help of cloning two completely identical groups, which will constitute a control group and a test group. Renard will also try to clone rabbits with the defective gene that causes cystic fibrosis. According to him, this gene in humans is similar to the one in rabbits, and "cloned rabbits will provide a better model for studying the disease, than other cloned species."
The cloned rabbits were born about a year ago, at the National Institute for Agronomic Research outside of Paris. Renard delayed the publication, in order to find out how many of them would reach adulthood, and to make sure that their health was normal. His research is described in a report that will be published today in the journal "Nature." Biotechnology.
Unlike normal fertilization, in cloning the embryo is created without the use of sperm. Instead, the scientists inject a nucleus from a "donor cell" into a denucleated egg. In the nucleus are the genes - and they direct the development of the embryo.
In cloning the rabbits, the researchers inserted a nucleus from a cumulus cell - cells attached to the egg - and inserted it into a rabbit egg. The nucleus and the egg were united using an electric current, which gave the signal to the egg to start dividing, and develop into an embryo. The resulting embryo was implanted in the uterus of a surrogate rabbit, where it continued to develop like a normal embryo. A rabbit born in such a process is a genetic twin of the adult rabbit from which the donor cell was taken.
Renard said that he started trying to breed rabbits about three years ago, but always failed. Attempts by other researchers also always ended in failure. In the current experiments, Renard tried to adapt the conventional cloning method to the breeding system of rabbits. For example, he discovered that the chemicals that are usually used to stimulate the development of the fetus in the laboratory (before it is implanted in the uterus), cause defects in the rabbits later in the pregnancy, so he only used them for half the usual time.
As with other animals cloned so far, success rates in attempts to clone rabbits have remained extremely low. Of the 775 cloned embryos created, only 371 survived to the stage where they could be implanted in the uterus. These embryos were implanted in 27 rabbits, in only 10 of which the embryo was absorbed and a pregnancy developed.
The pregnancy lasted until its end in only four rabbits, which finally gave birth to 6 live puppies. Two of the puppies died a day after birth.
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