Open in full screen mode Retro is the first cloned rhesus monkey to reach adulthood. Agence France -Press Chinese scientists have successfully cloned a rhesus macaque, now two years old and healthy, by refining the technique that gave birth to the sheep Dolly in 1996, according to a study published in the journal Nature. Communications(New window) (in English). Primates are particularly difficult to clone and scientists have faced years of difficulty ;fail before succeeding. They hope that their new technique, which uses the placenta, will lead to the creation of identical rhesus monkeys for medical research purposes. Since the Dolly sheep was cloned by the somatic cell nuclear transfer (SCNT) technique in 1996, more than 20 different mammals have been created through this process: dogs, cats, pigs and cattle.
Dolly the sheep presented to the media on February 22, 1997.
But it wasn't until 20 years later that scientists succeeded in cloning the first primate. A pair of genetically identical crab-eating macaques, named Hua Hua and Zhong Zhong, were born by SCNT in 2018 at the Institute of Neuroscience of the Chinese Academy of Sciences in Shanghai, led by Qiang Sun, first author of the study.
Hua Hua and Zhong Zhong
It was a scientific breakthrough, even though less than 2% of cloned crab-eating macaques were alive at birth. All attempts to clone rhesus monkeys (Macaca mulatta, a species which gave its name to the blood group system) had otherwise failed.
The team from the Chinese institute investigated the reasons for this failure and determined the main cause: the placentas providing nutrients necessary for the growth of the cloned embryos showed abnormalities compared to the placentas resulting from the in vitro fertilization of non-cloned monkeys.
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The researchers therefore replaced the cells of the future placenta, called trophoblast, with those from a healthy, uncloned embryo. This technique significantly improved the success rate of SCNT cloning and led to the birth of the cloned rhesus monkey. Named Retro, he is now two years old, Qiang Sun explained to AFP.
A downside: only one of the 113 initial embryos survived, a success rate of less than 1%, notes Lluis Montoliu, of the Spanish National Center for Biotechnology, who n& #x27;did not participate in the research.
If humans were to be cloned one day – the great fear in this field of research – it would first be necessary to successfully clone other species of primates, this scientist argues to Science Media British Center (SMC).
The low success rate of this research confirms that not only is human cloning unnecessary and questionable, but that it is ;he was tempted, it would be extraordinarily difficult and ethically unjustifiable, commented Lluis Montoliu.
An opinion shared by Qiang Sun, who considers the cloning of a human being unacceptable in all circumstances.
The technique of reproductive cloning by SCNT ( Somatic Cell Nucleus Transfer) involves producing a genetic copy of an animal by replacing the nucleus of an unfertilized egg with a cell from the (somatic) body of the donor animal, to form an embryo that can be transferred into the uterus of a surrogate mother.
A rhesus monkey named Tetra had already been cloned in 1999 with another technique using embryo division. A simpler process, but one that can only produce four clones at a time.
Scientists therefore focused on SCNT in part because x27;he can create many more clones, with the aim of creating genetically identical monkeys to study certain diseases and test drugs.