Scientific American, 1/98, Glenn Zorpette, page 26
Headless frog embryos are here. "So what?" biologists say
In the wake of a British biologist's assertion that he had created frog embryos that failed to grow a head, many of the alarmed pronouncements that made their way into the popular media seemed to have been informed by the weirder veins of pulp science fiction rather than by scientific plausibility. Press reports conjured up imagery of human organs growing in bottles and even mutant human "organ sacks" grown from headless embryos and kept alive artificially for the sole purpose of storing organs for harvesting and transplantation. At about the zenith of surreality, a former director of the National Institutes of Health reportedly noted on the CBS Evening News that a headless embryo would "have zero potential to say no."
Many biologists and ethicists, however, are far more troubled by the flights of morbid fantasy, which they say could have a chilling effect on potentially beneficial research. Some were also disturbed by what they perceive as the role of Jonathan Slack, a developmental biologist at the University of Bath, in fostering the wild speculation. "Slack unleashed a torrent of silliness at the expense of the scientific community," charges Arthur Caplan, an ethicist at the University of Pennsylvania. Slack declined to be interviewed for this article.
The furor began last October 19, when the London Sunday Times broke the news of Slack's achievement. By controlling signaling proteins known as fibroblast growth factors, Slack altered embryonic processes that are instrumental for the growth of the head, or of the trunk and tail, of the frog Xenopus laevis. He was therefore able to grow not only embryos with no head but also ones that were nothing but a head. The embryos were not kept alive beyond about three days, at which point an embryo has only precursors of most of the organs and has not yet begun to feed.
In his interviews with the local press, Slack observed that no biological principle would keep a technique similar to his from working on a human embryo. Thus, he said, it was time to ponder the possibility of a headless human, cloned and grown for the express purpose of providing any needed vital organs for its anatomically complete genetic donor "You can't stop things once they start, and it is sensible to talk about it now," he told the Daily Telegraph.
Media coverage quickly converged on what one biologist labeled the "yuk factor," with some ethicists and clergy members expressing horror and disgust. Biologists, on the other hand, were baffled by the outpouring of indignation. Genetically created headless embryos are not at all new. Headless frog embryos have been made by various pseudogenetic techniques since the early 1990s. And in 1994 headless mouse embryos resulted from studies of a gene known as Liml by William Shawlot and Richard R. Behringer of the M. D. Anderson Cancer Center in Houston. Second, legal restrictions in most of the developed countries prohibit the growth outside the womb, beyond a short period, of human experimental embryos.
Perhaps most important, the technical difficulty and impracticality of the scenario outlined by Slack, in comparison with other biotechnological approaches now being explored, essentially rule it out as a source of organs for transplant any time in the foreseeable future. According to Behringer, the idea of developing Slack's technique into something that could be used with humans is "a complete fantasy. I can't understand where this is coming from."
"To get it to work in humans," explains Brigid L. M. Hogan, a cellular biologist at Vanderbilt University Medical Center, "you would have to implant the partial embryo back into a woman, and no one would want to do that." Alternatively, it might be possible to culture embryos using some kind of artificial life-support system that could nurture the embryo for perhaps a couple of months, until rudimentary organs had been formed. Versatile cells known as stem cells could then conceivably be taken from these organs and used to repopulate and repair the corresponding damaged organ in a human. The only technical problem is that the life-support system called for in this scenario is far beyond current technology. "I cannot tell you how dopey it is, physiologically or cost-wise," Ca plan declares.
In the meantime, Caplan and other ethicists worry that potentially valuable offshoots from embryological research could be precluded if the public becomes overly exercised about the lurid science fiction. "We should not permit the nightmare visions to impede re search now," says ethicist Ronald M. Green of Dartmouth College. "Research on cell differentiation and the genetics of embryological development [has] great potential benefits." For example, a rare genetic disorder in humans called anencephaly can partly or completely block the development of the brain and head; it is possible that work such as Slack's could shed light on the condition-and its possible prevention.
"There's an impulse to prohibit, prohibit, prohibit," Green says. "We don't even know what we're prohibiting yet."