Kuo and Baxter are now working on the next step, which is to fuse a donor cell with the denucleated egg. A lid with appropriately positioned donor cells will be placed on top of the eggs. "Then they're ready to fuse," says Kuo, although he won't reveal details of the method. After fusion, eggs that develop far enough could be implanted manually into an animal's womb as normal.

"If it works with cow [eggs], that would be very neat," says Rudolph Jaenisch of MIT, who studies problems with cloning. But just because it works with sea urchins doesn't guarantee that it will work with the eggs of other species, he warns.

And Randall Prather of the University of Missouri, whose team recently announced the cloning of miniature pigs, says the chip won't help solve other problems, such as ensuring that the eggs you use have been kept in the right conditions. He thinks it might also be too expensive for many labs.

Kuo admits there is much work still to be done on the chip, but he believes it's worth the effort. One could submit different batches of eggs to various treatments, to find out which conditions improve success rates in cloning, he says. Such studies could also help researchers identify the factors in eggs that reprogram the added nucleus.

If the chip does improve success rates in animals, it is likely to be used to create cloned human embryos, where the problem is not dealing with many eggs at a time but getting hold of sufficient numbers of eggs. Companies such as Advanced Cell Technology hope to obtain embryonic stem cells from cloned embryos but have had only limited success (New Scientist, 1 December 2001, p 4).

The chips might also appeal to the mavericks who want to carry out human reproductive cloning despite all the warnings about the risks. The warnings are based on the health problems seen in the few clones that do survive, which have also prom
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Contact: Claire Bowles
claire.bowles@rbi.co.uk
44-207-331-2751
New Scientist
30-Jan-2002