Paris (AFP) – Chinese scientists have succeeded in cloning a now two-year-old healthy rhesus monkey by refining the technique used to give birth to Dolly the sheep in 1996, according to a study published on Tuesday.
Published on: 01/16/2024 – 7:27 p.m. Modified on: 01/16/2024 – 7:25 p.m
3 mins
Primates are particularly difficult to clone, and scientists had to fail for years before succeeding.
They hope their new technique, which uses the placenta, will lead to the creation of identical rhesus macaques for medical research.
Since Dolly the sheep was cloned using somatic cell nuclear transfer (SCNT) technology in 1996, more than 20 different mammals have been created using this technique: dogs, cats, pigs and cattle.
But it wasn't until twenty years later that scientists managed to clone the first primate. A pair of genetically identical crab-eating macaques named Hua Hua and Zhong Zhong were born in 2018 from SCNT at the Institute of Neuroscience of the Chinese Academy of Sciences in Shanghai, led by Qiang Sun, first author of the study published in Nature Communication.
A scientific breakthrough, even though less than 2% of the cloned crab-eating macaques were alive at birth. All attempts to clone rhesus macaques (Macaca mulatta, a species that gave its name to the blood group system) had otherwise failed.
Cloning humans “extraordinarily difficult”
The Chinese Institute team investigated the reasons for this failure. And identified the root cause: the placentas that provide the nutrients necessary for the growth of cloned embryos had abnormalities compared to the placentas that resulted from in vitro fertilization of non-cloned monkeys.
The researchers therefore replaced the cells of the future placenta, called trophoblasts, with those of a healthy, non-cloned embryo. This technique “significantly improved the success rate of SCNT cloning” and led to the birth of the cloned rhesus monkey. His name is Retro and he is now two years old, Qiang Sun told AFP.
Photo published by Nature Communications on January 16, 2024 of the cloned rhesus monkey named Retro, taken in 2023 at the Institute of Neuroscience of the Chinese Academy of Sciences in Shanghai © Qiang Sun / Nature Communications/AFP
One downside: Only one of the 113 original embryos survived, a success rate of less than 1%, notes Lluis Montoliu of Spain's National Center for Biotechnology, who was not involved in the research.
If humans were to one day be cloned – the great fear in this field of research – we would first have to succeed in cloning other primate species, argues this scientist from the British Science Media Center (SMC).
The low success rate of this research “not only confirms that human cloning is 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 human cloning to be “unacceptable” under any circumstances.
The SCNT (“Somatic Cell Nucleus Transfer”) reproductive cloning technique consists of creating 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 is capable of being transferred into the uterus of a surrogate mother.
A rhesus monkey named Tetra had already been cloned in 1999 using a different embryo division technique. A simpler process, but can only create 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.
© 2024 AFP