The US debate on human cloning gathered steam recently, moving toward federal legislation

that could affect both next fall's Congressional elections and the pre-eminence of US scientists in the worldwide race to turn research on human embryonic stem cells into a therapeutic revolution.

Testimony at a US Senate hearing on 5 March debated a bill proffered by Republican Senator Sam Brownback (Kansas) that would impose criminal penalties on all attempts at transferring a human somatic cell nucleus into a human egg, whether the purpose was to create an infant (usually called reproductive cloning) or to derive embryonic stem cells for disease research (usually called therapeutic cloning.) The US House of Representatives passed a similar total ban last year. Two other bills have also been introduced into the Senate; both would ban reproductive human cloning but permit therapeutic cloning.

Meanwhile, President Bush is expected to fill the long-vacant top job at the National Institutes of Health this week with Elias Zerhouni, executive vice dean of the Johns Hopkins University School of Medicine in Balthnore. For several months the front-runner for NIH director had been AIDS expert Anthony Fauci, head of the National Institute of Immunological Diseases and Stroke. The campaign against Fanci was led by Brownback, who regarded him as insufficiently pro-life. Zerhouni is said to have endorsed Brownbacks anti-cloning bill in writing.

The Bush administration also proposed last week that the United Nations adopt a Brownback type worldwide ban on human cloning, including therapeutic cloning. The UN is considering prohibiting reproductive cloning, but delegates from Europe and Asia oppose interfering with cloning to produce embryonic stem cells for research.

The US Senate hearing starred Christopher Reeve, Hollywood's former Superman, a persuasive high-profile advocate for stem cell research who is handsome as ever, but paralyzed from the shoulders down and unable to breathe on his own because of a riding accident some years ago. Testifying against the Brownback bill, Reeve told the hearing that only human embryonic stem cells carrying his own DNA offered hope for remyelinating his devastated spinal nerves via an immunologically compatible cell transplant. Also testifying against the bill was the hearing's scientific star, Nobel laureate Paul Berg of Stanford University. Berg argued that human stem cells not only could solve the problem of transplant rejections, they also could provide a unique source of information about common chronic late-onset diseases such as cancer. Studying cells from young people carrying mutations that predispose them to complex disorders could illuminate the disease process and generate clues to prevention or cure, he said. As both these applications are based on transfer of particular nuclei into human eggs, he pointed out, none of the existing 78 human embryonic stem cell lines President Bush approved for federally funded research last summer would be useful either for complex disease research or for compatible transplants.

Berg also objected strongly to both the Brownback and the House bills' ban on importing therapies based on human embryonic stem cell research done elsewhere in the world. That would prevent 280 million Americans from taking advantage of treatments developed in nations such as the UK where some of this research is permitted, he pointed out. It might even mean that Americans who seek such treatments abroad could be arrested and fined when they return, he predicted.

Both Reeve and Berg have suggested that a comprehensive ban on human cloning would put US scientists at a competitive disadvantage. The US would take a giant step backward in research leadership, Reeve noted, and anyway the work would be done abroad, for example in Europe. "Those are not rogue nations behaving irresponsibly," he told the Senate. Berg has said that h

A．Both reproductive and therapeutic cloning

B．Reproductive cloning only

C．Therapeutic cloning only

D．Neither reproductive nor therapeutic cloning