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By Jaclyn Jeffrey-Wilensky
When Chinese scientists added human genes to monkeys, they hoped to better understand how human brains develop. In so doing, they sparked an ethical debate on research that some believe would blur the line between humans and animals.
Scientists behind the new research, published March 27 in the journal National Science Review, claim that genetically modified monkeys can advance our understanding of brain development, which could lead to new treatments for cancer. Autism and other developmental disorders.
Critics of the research – including a scientist who contributed to it – called the project an offense, arguing that scientific gains did not warrant the creation of monkeys that could end up with a more human intelligence.
"My personal opinion is now that, from an ethical point of view, such research should not actually be conducted," Martin Styner, computer scientist at the University of North Carolina, Chapel Hill, who was doing part of the research team of scientists, told NBC News MACH in an email.
Still others say that, ethical pitfalls and all, genetically modified monkeys are our best hope of revealing the secrets of the brain and its disorders.
The conflict illustrates what Jessica Mayhew, director of the Primate Behavior and Ecology Program at Central Washington University in Ellensburg, calls the "ethical quagmire" of animal testing.
A simple question
The research was born of a simple question: how does our DNA have the model of the powerful brains of man? The scientists, based at the Kunming Institute of Zoology at the Chinese Academy of Sciences, wanted to understand the role of the MCPH1 gene in the development of the human brain.
Babies with defective copies of the gene are often born with unusually small heads, a condition called microcephaly. And since the human and monkey versions of MCPH1 are slightly different, scientists believe that the gene may be partly responsible for the high intelligence of humans.
In this study, scientists added the human version of MCPH1 to 11 embryos that would become rhesus macaques, with blond-dirty monkeys sharing about 93% of their DNA with humans. The so-called transgenic embryos were then implanted in the uterus of monkeys.
Two embryos were lost as a result of miscarriage; three others were euthanized before birth so that scientists could examine their brains. One of six born monkeys died about two months later. The other five had memory tests and their brains were imaged at regular intervals.
The transgenic monkeys behaved in the same way as their unchanged counterparts and their brains were about the same size. But their brain cells took longer to develop than unmodified monkeys – a sign that researchers have interpreted as neoteny, the very slow maturation of the human brain, thought to be linked to high intelligence. of our species.
They also outperformed unmodified monkeys in memory tests and had faster reaction times.
A link between intelligence and suffering?
The results led some to wonder if the MCPH1 monkeys were a little closer to consciousness.
Styner expressed concern that transgenic monkeys could be avoided by their unchanged counterparts, although he acknowledged that he had not observed the animals and had no expertise in genetics or genetics. Bioethics. Other experts echoed Styner's concerns.
"I do not think that all animal / human genetic hybridization experiments are unethical," said Arthur Caplan, bioethicist at the NYU School of Medicine. "Inserting human genes into the brain of monkeys is another matter." Like Styner, Caplan felt that the study was likely to create something that was not human, but not quite a monkey.
But Megan Dennis, a biochemist and geneticist at the University of California at Davis, said insertion of a human gene was probably not enough to give monkeys self-awareness.
"Rhesus monkeys are sufficiently evolutionary in humans that some gene additions do not create a" planet of the apes "scenario," she said, referring to fears that transgenic monkeys could take consciousness of themselves.
Built-in protections
Rhesus monkeys and other monkeys of the Old World can be a useful model for the study of the human brain. Their brain is much more similar to the human brain than other common research animals, such as mice. And with 25 million years of evolution separating them from humans, they are considered less ethical to use in experiments than chimpanzees and other great apes, who share with humans nearly every percentage point of their genome.
"Rhesus macaques are one of the best animal models to study the development and evolution of the brain and have the best translational value for improving human health," said Anthony Chan, a researcher at the Yerkes Primate Research Center. from Emory University, in an email. But, he added, scientists need to be cautious when they add human genes to animals, designing their experiments in ways that minimize their suffering.
In 2015, the National Institutes of Health announced that they would no longer support biomedical research on chimpanzees. Research on great apes is either prohibited or restricted in many places, including in countries of the European Union.
In the United States, the National Institutes of Health fund both monkey research and research involving the introduction of human genes into animals. NIH has awarded 249 grants to support non-human primate research in 2017, Science magazine reported. Nevertheless, research is often less expensive and more practical in China than in the United States, making it a breeding ground for genetics research in apes.
Another scientist involved in the new study, Bing Su of the Kunming Institute of Zoology, said in an email that the institute's ethics committee had approved the study and that the monkeys were treated in accordance with international standards. He added that, apart from the rate of development of their brain, transgenic monkeys were not very different from their unmodified counterparts.
"In theory and in reality, there is no" humanity "observed in the transgenic monkeys MCPH1, since only one gene has been modified among tens of millions of genetic differences between man and monkey," he said. -he declares.
Regarding the doubts of his co-author, Su stated that Styner had never expressed any personal concerns to him, and that when he had learned that their research had been published, Styner replied by e-mail: " Congratulations to all the team !! "
"With two exclamation points," Su said.
For his part, Styner said he would only decide later on the ethics of the experiment. "This is the first time I regret sending such a congratulatory e-mail," he wrote about the exchange.
The five surviving monkeys would be in good health.
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