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Introducing Retro, a rhesus macaque clone born on July 16, 2020.
He is now over 3 years old and “growing well and growing strong,” said Fallon Lu, one of the authors of a research paper published Tuesday in the journal Nature Communications explaining Retro’s birth. “I’m doing it.”
Retro is only the second species of primate that scientists have successfully cloned. The same research team announced in 2018 that it had created two identical cloned cynomolgus monkeys (a type of macaque) that are still alive today.
“We have successfully cloned a living, healthy rhesus macaque monkey for the first time. This is a huge step forward, turning the impossible into possible, but the efficiency is very low compared to normal fertilized embryos.” said Lu, a researcher at the National Key Research Institute. Institute of Molecular Developmental Biology and Genetic and Developmental Biology, Chinese Academy of Sciences. “As of now, I have not given birth to my second child yet.”
The first mammal to be cloned, Dolly the sheep, was created in 1996 using a technique called somatic cell nuclear transfer (SCNT). Scientists essentially reconstruct an unfertilized egg by fusing the nucleus of a somatic cell (rather than from a sperm or egg) with an egg from which the nucleus has been removed.
Since then, scientists have cloned many mammals, including pigs, cows, horses, and dogs, but the process is hit or miss and usually results in viable offspring that are implanted into surrogate mothers. Only a few embryos are born.
“Since Dolly, many mammal species have been cloned, and in some ways great progress has been made, but the fact is that inefficiency remains a major obstacle.” said Miguel Esteban, lead researcher. Academy of Sciences. Although he was not involved in the latest study, he has collaborated with some members of the research team on other primate studies.
A Chinese team based in Shanghai and Beijing used a modified version of SCNT in a study of cynomolgus monkeys (Macaca fascicularis) and further tweaked the technique to clone rhesus monkeys (Macaca mulatta).
After hundreds of failed cloning attempts, they realized that the outer membranes that form the placenta had not developed properly in early cloned embryos. To address this problem, they performed a process called internal cell mass transplantation. This involved putting cloned internal cells into an uncloned embryo, which allowed the clone to develop normally, Esteban explained.
The researchers then tested the new technique using 113 reconstructed embryos, 11 of which were implanted into seven surrogate mothers, resulting in only one live birth. .
“We believe there are additional possibilities…anomalies to correct. Strategies to further increase the success rate of SCNT in primates…remain our main focus going forward,” Lu said. Ta.
The first two cloned monkeys, Zhong Zhong and Hua Hua, are now over six years old and are living “happy and healthy lives” with other monkeys of their kind. Lu said that so far researchers have not identified any potential limits to the lifespan of cloned monkeys.
Zhong Zhong and Hua Hua are usually described as the first cloned monkeys. However, a rhesus monkey was cloned in 1999 using what researchers believe to be a simpler method of cloning. In that case, rather than using adult cells as in SCNT technology, scientists split the embryos, similar to what happens naturally when identical twins develop.
Researchers said success in cloning monkeys could help accelerate biomedical research, given the limits to what scientists can learn from laboratory mice. A report by a committee of the National Academies of Sciences, Engineering, and Medicine released in May found that research in nonhuman primates, which are similar to humans, is critical to advances in life-saving medicine, including the development of vaccines against COVID-19. It’s important.
The use of monkeys in scientific research is a controversial issue due to ethical concerns regarding animal welfare. The research team said it followed Chinese laws and guidelines governing the use of non-human primates in scientific research.
The Royal Society for the Prevention of Cruelty to Animals said there were “serious ethical and welfare concerns regarding the application of cloning techniques to animals”. Cloning animals requires painful and painful procedures and can have high failure and mortality rates. ”
Esteban said it might be useful to be able to create genetically identical monkeys.
“This study provides proof of principle that cloning is possible in a variety of non-human primate species, and opens the door to new ways to increase efficiency. “You can genetically manipulate them in a way that has many implications for disease modeling. There’s also a species conservation perspective,” he added.
Dr. Luis Montoliu, a researcher at Spain’s National Center for Biotechnology (CNB-CSIC) who was not involved in the study, said cloning both monkey species demonstrated two things.
“Firstly, it is possible to clone primates. And secondly, just as importantly, the efficiency is so low that these experiments are very difficult to pull off,” he said. said in a statement.
He said the low success rate of the process “demonstrates that human cloning is not only unnecessary and controversial, but also extremely difficult and ethically unjustifiable if it were attempted.” he added.
“Reproductive human cloning is completely unacceptable,” Lu said.