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The researchers added a human gene related to the brain development of our species to 11 monkey embryos in order to study its impact on brain growth, triggering an international debate on the ethics of animal experimentation that saw one of the co-authors of the study condemning his own contributions to research. .
Human brain gene added to Rh macs to study brain development
A new report from NBC News MACH describes how scientists in China and the United States are investigating a gene related to the development of the human brain and how it affects brain growth by exchanging the version of the gene found in macaques rhesus with the one found in humans. Publication of their results in the journal National Science Journal has sparked international controversy, even one of the study's coauthors now claiming that research was crossing a critical line of ethics.
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The research was designed to examine a specific gene, MCPH1, which humans share with other primate species and is associated with brain development and the extent to which this gene is responsible for the size of the human brain. We know that there is a link between the two, since an abnormal MCPH1 gene often causes a disease called microcephaly, leading to children born with an abnormally small head.
Of the 11 embryos modified by the scientists, two were lost due to miscarriage and three of the pregnancies were interrupted before birth so that the brains of Rhesus fetal macaques could be studied. Six of the monkeys were completed, although one died a few weeks after birth. Of the five surviving monkeys, memory tests and brain tests were performed regularly to assess their brain development. Research revealed that monkeys behaved normally and that their brains were as large as an unaltered macaque brain, but macaques with the human version of MCPH1 demonstrated better memory than their peers and their reaction times were also faster.
They also found that the brain cells of macaques carrying the human MCPH1 gene grew much more slowly than the cells of their unmodified peers, which is similar to the slow development of the brain for which humans are known, which may be the key to our higher level of intelligence.
Does changing the cerebral development of monkeys go beyond an ethical line?
Rhesus macaques are not as close to humans in terms of evolution as the great apes species, such as chimpanzees and gorillas, and they diverged from human beings there are about 25 million d & # 39; years. Nevertheless, they share more DNA with humans – about 93% – than other animals and, of course, they are still primates. Their brains are much more similar to ours than other animals used in research, such as mice.
"My personal opinion is now that, from an ethical point of view, such research should not actually be done." – Martin Styner, co-author of the study
"Rhesus macaques are one of the best animal models for studying brain development and evolution and have the best translational value for improving human health," said Anthony NBC, a researcher at the Yerkes National Primate Research Center of the Emory University. Nevertheless, he warned that any study that adds human genes to animals must be carefully constructed in order to minimize the suffering of the animal.
Bing Su, of the Kunming Institute of Zoology and co-author of the study, told NBC that the study had been the subject of a thorough ethical review before to start and that the scientists involved followed all international standards for animal testing.
"In theory and in reality, there is no" humanity "observed in transgenic MCPH1 monkeys," he said, "because a single gene has been modified among tens of millions of genetic differences between humans and humans. monkeys".
At the same time, another scientist involved in the study, Martin Styner, computer scientist at the University of North Carolina at Chapel Hill, has since rejected his own participation in the study, which he says goes beyond the limits of ethics. In an email to NBC News, he wrote, "My personal opinion is now that, from an ethical point of view, such research should not actually be done."
The scientists conducting the research believe that many diseases and disorders affecting the brain can be treated if the actual development of the brain is better understood and the most effective way to achieve this understanding is to use genetically modified monkeys.
The ethical debate is not new
Our discomfort with ethics is not entirely new either. Arguments against a genetic modification of the monkey brain could reasonably be applied to all animal tests. Medical investigations of different diseases and biological structures regularly modify other living organisms to meet the needs of medical research as a common practice.
A superficial examination of medical research done on mice would be overwhelming evidence of crimes against humanity when committed against humans rather than rodents. Different diseases or genetic disorders, including cancers and other painful diseases, are regularly administered to mice and the brain of these mice has long been the subject of studies by genetic alteration, not to mention direct manipulation by electrodes or by other similar means.
Those who support controversial animal testing often point out that those who oppose their research but not other animal research do not really oppose a new ethical violation; they oppose the ethical violation that has always existed, we could simply move away from it because it only happens to mice.
The realization of this same research on species more closely related to humans makes this ethical violation inevitable for those who would rather ignore it in the name of progress. What people are objecting to is not that the search for one animal over another is ethically distinct, they oppose research on animals themselves, but are uncomfortable with their conscious and deliberate use of the practice when they can benefit from it.
Others recognize the ethical dilemmas involved in animal testing in general, but can still distinguish cases and find one more deplorable than the other ethically. The issues of pain and self-awareness must be taken into account. To say that all the tests on animals are the same, it is to level all life as equally sacrosanct, which very few people believe to be the case.
If that was the case, following antibiotic treatment would mean carrying out slaughter orders of a magnitude greater than that of the Holocaust, while we poison billions of organisms. alive until death. Eradicating an illness would be like genocide. However, Jonas Salk was not tried for his crimes but celebrated for the creation of the polio vaccine.
No one mourns the destruction of the smallpox virus and the arguments for the eradication of certain dangerous species, such as mosquito vectors of malaria, are not based on moral reasons but on practical reasons. The arguments against the elimination of mosquitoes, as many have advocated, point out that this will have an unpredictable effect on the food chain and the environment; the immorality of exterminating an entire species, whose only crime is to maintain its vital functions, only rarely enters the debate.
Why rhesus macaques feel different from people compared to other animals used in research
Understanding how our genes establish the biological plan for the development of the unique human brain is an important part of the answer to one of the most basic and unanswered questions regarding our species, while providing a framework that we can use to create medical treatments. for brain disorders.
It's the unique quality of our brains that allowed Homo sapiens outperform all other known species on the planet, extinct and extant, while only arriving on the scene in relation to time scales of evolution. The impact of humanity on the planet has been so profound that we have spurred a geological change normally reserved for the impacts of asteroids or comets killing the planet.
As such, identifying what change in our DNA has caused such a monumental change in our biology is an important question to know who we are as a species. However, at some point, our answer to this question will say as much about us, if not more, than what is coded in our DNA.
The introduction of a human gene related to the development of the human brain in a close relative close to a primate has the potential to produce something that does not reach the level of the l '. human intelligence or self-awareness as we understand it, but which transcends its species in a radical way. important way. We know that the evolutionary leap of intelligence is radically different from any other biological change, we are living proof of it. What does it mean to give this jump to another species arbitrarily?
"I do not think all hybrid animal / human genetic experiments are unethical," said Arthur Caplan, bioethicist at NYU School of Medicine, at NBC News. "Inserting human genes into monkey brains is another matter." In doing so, he feared, he might create something non-human, but not a monkey either in the kingdom that humans consider sacred, our sense of intelligence and our self-awareness.
In the end, this nebulous gray area in the middle that such an animal would occupy – without it being his fault – is what worries most people. Not knowing what the animal understands of itself or of ourselves, or whether it understands what is happening to it, means that we do not know where we are in relation to the moral calculation that we usually use. However, as long as there are diseases and disorders of the brain, these assessments will continue to fuel controversy and the need to balance the needs of humanity and our moral responsibility towards the people. Animals that are at the mercy of our intelligence will continue to be. one of the great ethical challenges of our time.
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