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By Jaclyn Jeffrey-Wilensky
When scientists in China added human genes to monkeys, they hoped to gain a better understanding of how human brains develop. In the process, they provoked an ethical debate about the research that, according to some, blurs the line between humans and animals.
The scientists behind the new research, which was published on March 27 in the National Science Review, say that genetically altered monkeys can improve our understanding of brain development, which could lead to new treatments for autism and other disorders of the brain. developing.
But critics of the research, including a scientist who contributed to it, have declared themselves wrong, arguing that the scientific gains do not justify the creation of monkeys that could end up with an intelligence more similar to the human one.
"My personal opinion is now that, from an ethical point of view, such research should not be done," Martin Styner, a computer scientist at the University of North Carolina, Chapel Hill, who was a member of the team of scientists behind. The investigation told NBC News MACH in an email.
Others say that ethical traps and everything, genetically altered monkeys are our best hope to discover the secrets of the brain and its disorders.
The conflict illustrates what Jessica Mayhew, director of the primate ecology and behavior program at Central Washington University in Ellensburg, calls the "ethical quagmire" of animal testing.
A simple question
The investigation arose from a simple question: how does our DNA present the plan for the powerful brains of humans? Specifically, the scientists, based at the Kunming Institute of Zoology of 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 known as 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 the study, the scientists added the human version of MCPH1 to 11 embryos that would become rhesus macaques, dirty blond monkeys that share approximately 93 percent of their DNA with humans. The so-called transgenic embryos were implanted in the uterus of the monkeys.
Two embryos were lost to miscarriage; Three more were sacrificed before birth so that scientists could examine their brains. Of the six monkeys that were born, one died approximately two months later. The other five had memory tests and images of their brains were taken on an MRI machine at regular intervals.
The transgenic monkeys behaved very similarly to their unchanged counterparts, and their brains were approximately the same size. But its brain cells took longer to develop compared to those of the unaltered monkeys, a signal that the researchers interpreted as neoteny, the super slow maturation of the human brain that is believed to be linked to the high intelligence of our species.
They also outperformed unaltered 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 one step closer to something like consciousness.
Styner said he was concerned that transgenic monkeys could be rejected by their unaltered counterparts, although he acknowledged that he did not observe the animals and had no experience in genetics or bioethics. Other experts echoed Styner's concerns.
"I do not believe that all animal / human genetic hybrid experiments are unethical," Arthur Caplan, a specialist in bioethics at the New York University School of Medicine, said in an email. "Inserting human genes into the brains of monkeys is a different matter." Like Styner, Caplan felt that the studio ran the risk of creating something that was not human, but not a monkey.
But Megan Dennis, a biochemist and geneticist at the University of California at Davis, said the insertion of a human gene was probably not enough to give monkeys something like self-consciousness.
"Rhesus monkeys are evolutionary enough for humans that some gene additions do not create a 'Planet of the Apes' scenario," he said, referring to fears that transgenic monkeys might be self-conscious. same.
Rhesus monkeys and other Old World monkeys can be a useful model for studying the human brain. Their brains are much more like those of humans than those of other common research animals, such as mice. And with 25 million years of evolution that separates them from humans, they are considered less ethically risky to use in experiments than chimpanzees and other great apes, which share with humans almost all percentage points of their genomes.
"Rhesus macaques are one of the best animal models to study the development and evolution of the brain, and they have the best translation value to improve human health," said Anthony Chan, a researcher at the Yerkes National Primate Research Center of the Emory University, in an email. But, he added, scientists must be careful when adding human genes to animals, designing their experiments to keep suffering to a minimum.
In 2015, the National Institutes of Health announced that they would no longer support biomedical research in chimpanzees. Research on great apes is prohibited or restricted in many places, including the nations of the European Union.
In the United States, the National Institutes of Health funds research on monkeys and research that involves the introduction of human genes into animals. NIH awarded 249 grants to support non-human primate research in 2017, Science magazine reported. However, research is often cheaper and more convenient in China than in the USA. UU., What turns the country into a focus of genetic research in monkeys.
Another scientist involved in the new study, Bing Su of the Kunming Institute of Zoology, said in an email that the institute's ethics board had approved the study and that the monkeys were managed in accordance with international standards. He added that, apart from the rate of development of his brain, the transgenic monkeys were not very different from their unaltered counterparts.
"In theory and in reality, we do not see" humanity "in the transgenic monkeys MCPH1, since only one gene was modified among tens of millions of genetic differences between humans and monkeys," he said.
Regarding the co-author's misgivings, Su said that Styner never expressed any personal concern, and that when he learned that his research had been published, Styner sent back the email: "Congratulations to the entire team! "
"With two exclamation marks," Su said.
For his part, Styner said he had not decided on the ethics of the experiment until later. "This is the first time I regret sending a congratulatory email," he wrote when asked about the exchange.
The five surviving monkeys are in good health.
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