Test Monkeys' Offspring Pick Up Genetic Modification
Thursday, May 28, 2009
Scientists have created the first genetically modified monkeys that can pass their new genetic attributes to their offspring, an advance designed to give researchers new tools for studying human disease but one that raises many thorny ethical questions.
In this case, Japanese researchers added genes that caused the animals to glow green under an ultraviolet light -- and beget offspring with the same spooky trait -- to test a technique they hope to use to produce animals with Parkinson's, Huntington's and other diseases.
The work, described in today's issue of the journal Nature, was hailed by some medical researchers as a long-sought milestone that could lead to crucial insights into many ailments and provide invaluable ways to test new treatments.
But because the work marks the first time members of a species so closely related to humans have had their genetic makeup permanently altered, the research set off alarms that it marked a troubling step toward applying such techniques to people, which would violate a long-standing taboo.
"It would be easy enough for someone to make the leap to trying this on humans," said Lori B. Andrews, who studies reproductive technologies at the Illinois Institute of Technology's Chicago-Kent College of Law. "If you make this kind of change, it's passed on to all future generations. Many people think it's hubris to have people remaking people in this way."
The approach could tempt some to use the technique to try to engineer desirable traits in people, creating a society of genetic haves and have-nots, Andrews said. Others worried that the work could have additional disturbing implications, such as potentially blurring the line between species.
"It's hard to put your finger on what is it about this research that is likely to stimulate ethical debate besides the sort of gut feeling that this is not the right thing to do," said Mark A. Rothstein, a bioethicist at the University of Louisville. "But I think we'd better contemplate where this research is going and develop policies to deal with it before it slaps us in the face."
Scientists have genetically engineered many other species to be research tools. Mice in particular have been created with a wide assortment of characteristics and diseases that mimic human ailments. But because mice are so genetically different from humans, scientists have long sought to breed primates to provide better disease "models." Although scientists have been able to genetically modify individual monkeys, they had never been able to make the new traits hereditary -- a crucial step for breeding large enough numbers of research animals.
In humans, researchers have tried to correct genetic defects in individual patients, but there has always been a strict prohibition against making changes that would be passed on.
In the new work, Erika Sasaki of the Central Institute for Experimental Animals in Kawasaki and her colleagues conducted experiments using marmosets, small monkeys common in South America that mature and reproduce quickly.
The researchers modified a virus called a lentivirus to carry a jellyfish gene known as GFP (green fluorescent protein) into the genetic material of the marmosets' cells. The gene is widely used in research because it is easy to track -- cells in which the gene is active glow green when exposed to ultraviolet light.
The researchers used the genetically engineered virus to insert the jellyfish gene into 80 marmoset embryos, which they then transferred into the wombs of 50 females. Seven pregnancies resulted in five offspring, four of which showed signs of the jellyfish gene in their hair roots, skin, blood cells and other tissues. Under ultraviolet light, the skin on the soles of their feet glowed green.