Several animals, with the exception of primates, have been successfully cloned by scientists since Dolly the sheep. Now, rhesus monkeys that are two years old have supposedly been cloned in China.
Embryos and neonates perish in the majority of monkey cloning efforts because of the complexity of the process. But now scientists in China say they’ve successfully cloned a two-year-old rhesus monkey. Retro, the male animal, is active and in good condition. The announcement was made in a study that appeared in the peer-reviewed journal Nature Communications.
Scientists have used Somatic Cell Nuclear Transfer (SCNT) to clone over 20 different mammalian species, including pigs and cows, since the birth of the first cloned sheep, Dolly, in 1996. However, this strategy was always a failure when dealing with monkeys.
Additionally, cloned animals have a poor survival rate; the sole exception being cows. A lot of people have their lives cut short because they hurt their muscles or organs badly. Even with the small number of live-born cloned monkeys, this was the case. Before Zhong Zhong and Hua Hua, two cloned monkeys who ate crabs, were unveiled in early 2018 at Shanghai’s Institute of Neuroscience of the Chinese Academy of Sciences. A sensation, the two monkeys were. Even this new success story has its roots in the original institute.
Is this research making progress?
Chinese researchers found that cloned embryos’ placentas, which provide nutrition for their development, differed from placentas derived from in vitro fertilization of non-cloned monkeys.
A healthy, non-cloned embryo’s cells were then transplanted into the placenta to take its place. A cloned rhesus monkey was born as a consequence of the method, which enhanced cloning using SCNT.
“The study and technology presented in it are a very special and biologically very interesting story,” remarks Rüdiger Behr, a scientist who works on stem cell and embryo research at the German Primate Center. “I have my doubts that something new has been demonstrated here that could have broad application in the scientific community.”
Chinese researchers allegedly used a method that is capable of being executed by just a few of facilities globally, as stated by Behr. An embryo was generated using a mix of cloned and non-cloned components. It is already quite challenging to develop a cloned embryo.
What is the process of cloning and what makes it so challenging?
Most cloned animals have a shorter life expectancy and worse health, demonstrating the difficulty of making a perfect genetic replica, or clone, of a complex living creature.
Nuclear transfer from one kind of cell to another involves removing the nucleus from one type of cell and then transplanting it into another type of cell, such as an egg cell, in a process known as somatic cell nuclear transfer. “If the nucleus of a somatic cell is transferred to an enucleated egg, the egg is able to restore that somatic cell nucleus to a state that functions like a fertilized egg,” Behr says.
After fertilization, the egg starts to split and make more eggs. However, the embryonic cells undergo intense differentiation, eventually becoming cells of the skin, heart, muscles, or nervous system. All of these cells have the identical DNA stored in their nucleus. However, not every gene is readable. That is the only explanation for the diversification of cell kinds.
The nucleus of the implanted body cell is reprogrammed by the egg so that all of the genes may be read again. At least in principle, when an egg cell divides, it resets the cell’s nucleus, much like a computer. That doesn’t always work, as biologist Behr points out. This is the reason why the efficiency of cloning remains poor.
Is cloning primates more difficult?
One live birth was seen out of 484 embryos used in this investigation, proving that it is efficient. In Behr’s opinion, it’s very unlikely that the new procedure was the cause of the birth or that it was just a coincidence.
But according to Rüdiger Behr, “There are very few institutions in the world that are capable of carrying out such experiments with primates.” So, cloning primates isn’t more complicated than cloning other species. We have limited experience with cloning monkeys, therefore I think cloning is a tough process. Unlike, say, mouse research, breeding monkeys is a laborious and costly process. According to Behr, development has also been little in this regard.
Monkey cloning: why?
Monkeys that have been cloned are of great interest to researchers. Many disorders, including Alzheimer’s and Parkinson’s, are studied using these animals due to their similarities with people. The findings would be more reliable if they were derived from a group of cloned monkeys.
“When I was a PhD student, I couldn’t accept that monkeys could be cloned,” Behr says. Since they are near to people and very sensitive to suffering, he saw this as an ethical barrier.
“Now that my perspective has broadened, I believe that there are scenarios in which cloning monkeys may be a reasonable option. One such scenario would be the pursuit of medicines for incurable illnesses that cause immense misery, for which now no medication exists. According to Behr, they may also be used as gene treatments for conditions such as blindness, deafness, heart disease, and metabolic diseases.
However, the efficacy of studies using cloned monkeys in alleviating or preventing pain remains unknown. Consequently, Behr is wary: “it might work, but I don’t know.”