By Sylvia Pagán Westphal

Handmade cloning, a new way to create genetically identical copies of animals, is not only cheaper and simpler than existing methods, but appears to work better too.

"It's so much simpler than anything we are doing today, it's dramatic," says Michael Bishop, ex-president of Infigen, a cattle-cloning company in Wisconsin. "It's a huge step towards roboticising the whole process."

Fusing Half-Eggs With A Cell Creates An Embryo

The technique could speed up the introduction of cloning in farming, where the aim is to clone the best milk or meat-producing animals. And conservationists in South Africa could soon use it to clone endangered species.

The technique was developed by Gábor Vajta at the Danish Institute of Agricultural Sciences in Tjele together with Ian Lewis, programme leader for the Cooperative Research Centre for Innovative Dairy Products in Australia. Details of the method will soon be published.

Micro Manipulator

At the moment, the key instrument in cloning is the "micromanipulator", an expensive machine that allows a skilled technician to grab an egg cell under the microscope, insert a very fine needle to suck out its nucleus, and then use another needle to transfer a nucleus from the animal to be cloned. An alternative is to fuse the empty egg with a cell from the animal. Either way, it is a tricky and time-consuming process.

Fusing half-eggs with a cell creates an embryo (Click Image to Enlarge)

Fusing half-eggs with a cell creates an embryo

In the new technique, egg cells are split in half under a microscope using a very thin blade (see graphic). The halves quickly seal up. A dye is used to identify the halves containing the nucleus, which are then discarded, leaving only empty "cytoplasts". To create a cloned embryo, a cell from an adult animal is fused first with one cytoplast, then another, by briefly zapping them with an electric current.

Half of the cow embryos created this way survive long enough to form balls of cells called blastocysts, ready to be implanted in the womb. That success rate is at least as good as current standards.

But the big advantage this method has over normal cloning is that it you can use relatively cheap equipment, and personnel can be trained very quickly. It should be a boon to researchers on tight budgets, Vajta says. It should also be far easier to automate. Some companies are already trying to develop chips that mass-produce cloned embryo.

Healthy Looking

A healthy-looking calf created by handmade cloning has already been born in Australia, and another is expected this week. In preliminary tests, the Danish researchers implanted seven cow blastocysts, resulting in six pregnancies. After 150 days - the threshold after which cattle pregnancies usually carry to term - three are still pregnant.

By comparison, a recent paper suggests an average of only 25 per cent of cows implanted with embryos cloned the standard way are pregnant after 30 days.
It is too early to tell whether the animals created using this new technique will be healthier than those from normal cloning, which often fail to carry to term or have birth defects. But Vajta thinks the reduced manipulation times and the use of two cytoplasts should yield better results.

In the normal method, up to a third of the egg's cytoplasm can be lost when the nucleus is removed, whereas fusion with two cytoplasts produces embryos with the same volume as the original egg.

Field Test

In July, Paul Bartels and his team from the Endangered Wildlife Trust in Johannesburg tried out the method under field conditions. A Bunsen burner on a lab bench served as the sterile working area, and the most expensive piece of equipment was the electrofusion machine, still relatively cheap at $3500. "One can set up a lab very cheaply. You can imagine doing this in a trailer," he says.

The team fused cow cytoplasts with adult cells from endangered species such as the darted buffalo, the bontebok (a kind of antelope), the giant eland and the black impala. "We were very surprised at the health of the embryos. They looked so good," Bartels says.

The team also put five cloned cow embryos into three cows. If this results in healthy calves, they will consider cloning endangered species using closely related common species both as a source of eggs and as surrogate mothers.

Another advantage of the method is that it may bypass existing cloning patents. One worry, however, is that the method's simplicity will make it easier for maverick doctors to attempt human reproductive cloning. But there is one deterrent. They will need twice as many eggs as normal - and human eggs are in very short supply.

New Scientist August 14, 2002