After years of fiddling with human, mouse, rabbit, and cow cells, researcher Robert Lanza has declared that it’s impossible to create human-animal hybrid embryos, but that human cloning appears to be eminently doable.
Lanza wasn’t trying to create some freakish chimera, nor did he intend to bring forth a squalling baby as the world’s first human clone. But ever since researchers cloned Dolly the sheep in 1996 by transferring the nucleus of one of her cells into the nucleus-free egg of another sheep, scientists, ethicists, politicians, and the public have wondered whether a person could be cloned in the same way [ScienceNOW Daily News]. While human cloning has largely been rejected as unethical, many researchers are excited by the idea of “therapeutic” cloning, in which the same technique could be used to create embryos that would be harvested for medically useful stem cells. Those stem cells would have the same genetic profile as a patient and would thus avoid immune-rejection issues [ScienceNOW Daily News].
Because of the shortage of human egg donors, the hybrids were proposed as a way of creating large numbers of human embryo clones to harvest stem cells in bulk [Telegraph]. Lanza’s stem cell company, Advanced Cell Technology, has spent several years inserting human nuclei into egg cells from mice, rabbits, and cows, but all of the thousands of embryos they created in this way failed to develop. “At first we thought it would just be a matter of tweaking the culture conditions,” says Lanza. But “the problem was far more fundamental” [Nature News].
The hybrid embryos looked fine initially, but they quickly fizzled, Lanza reported in the journal Cloning and Stem Cells. A mouse-human hybrid petered out after just one [cell] division. The cow and rabbit human hybrids went further, but stopped at the point when maternal DNA is supposed to kick in and turn the ball of cells into a proper embryo, Lanza said [Reuters]. However, some stem cell researchers say that Lanza’s results don’t definitively prove that hybrid embryos are a dead end, and say that a hybrid using two closely related species, like humans and primates, might fare better.
Finally, about that human cloning: in the same study, Lanza notes that a human nucleus inserted into a different human’s egg cell appears to develop normally. “We show for the first time that the same genes turned on in normal human embryos are the same genes turned on in human clones” [Wired News], he says. If Lanza’s study holds up to further scrutiny, it will mean that there are no technical barriers to therapeutic or reproductive cloning. Which means, some experts say, that it’s just a matter of time before someone tries to make a genetic copy of themselves.
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