2024-01-16 18:27:08
Published on: 01/16/2024 – 7:27 p.m. Modified on: 01/16/2024 – 7:25 p.m.
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Primates are particularly difficult to clone and scientists faced years of failure before succeeding.
They hope their new technique, which uses the placenta, will lead to the creation of identical rhesus monkeys for medical research.
Since Dolly the sheep was cloned using the somatic cell nuclear transfer (SCNT) technique in 1996, more than 20 different mammals have been created using this process: dogs, cats, pigs and cattle.
But it was only twenty 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 published study in Nature Communications.
A scientific breakthrough, even if 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.
Human cloning ‘extraordinarily difficult’
The Chinese Institute team investigated the reasons for this failure. And identified the main cause: the placentas providing nutrients necessary for the growth of cloned embryos presented anomalies compared to the placentas resulting from the in vitro fertilization of non-cloned monkeys.
Photo released on January 16, 2024 by Nature Communications of the cloned rhesus macaque, named Retro, taken in 2023 at the Institute of Neuroscience of the Chinese Academy of Sciences in Shanghai © Qiang Sun / Nature Communications/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 did not participate in the research.
If humans were to be cloned one day – the great fear in this field of research – we would first have to succeed in cloning other species of primates, argues this scientist at the British Science Media Center (SMC).
The low success rate of this research “confirms that not only is human cloning unnecessary and questionable, but that if it were attempted, 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 SCNT (“Somatic Cell Nucleus Transfer”) reproductive cloning technique consists of 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 to 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 which can only produce four clones at a time.
So scientists have focused on SCNT in part because it can create many more clones, with the goal of creating genetically identical monkeys to study certain diseases and test drugs.
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