January 16, 2024

expert reaction to study reporting that Chinese researchers have successfully cloned a rhesus monkey

A new study published in Nature Communications reports the successful cloning of a rhesus monkey. 

Prof Robin Lovell-Badge FRS FMedSci, Group Leader, Francis Crick Institute, said:

“With only one live macaque obtained after the procedures used, it is impossible to give any rate of success – so claims to have a better technique are unjustified. The method to replace the trophectoderm to give a placenta derived from non-cloned cells is obvious, although it introduces an added level of complexity (and more macaques are required to provide eggs that are fertilised to give early embryos from which the outer trophectoderm layer is isolated). But even using this, the methods are still very inefficient and lead to many miscarriages. The methods do not get us any closer to reproductive cloning in humans – which has always been a nonsense idea. It would be unethical purely on grounds of safety. But also why would anyone want to clone a person? The clone might look rather similar to the original person donating the cells used for somatic cell nuclear transfer, much like ‘identical twins’ are very similar (although usually readily distinguishable), but they will not have the same character, etc, etc, as we are not just a product of our genes.”

The following comment was provided by our friends at SMC Spain:

Dr Lluís Montoliu, researcher at the National Center for Biotechnology (CNB-CSIC) and CIBERER-ISCIII, says:

“On July 5, 1996, at the Roslin Institute near Edinburgh, the sheep Dolly was born, the first cloned animal from adult cells. However, the world wouldn’t know about it until February 1997 when this biological feat was reported in a historic and controversial article in the journal Nature, sparking the imagination and fears of half of humanity. If it was possible to clone sheep, why wouldn’t it be possible to clone humans?

“In reality, those fears were entirely unfounded. Cloning other mammal species became a slow drip that demonstrated the intrinsic difficulties of each species, with distinct characteristics in their reproductive biology necessary to adapt the original method developed to clone Dolly the sheep. Cows and mice were cloned in 1998, goats in 1999, pigs in 2000, cats and rabbits in 2002, rats and horses in 2003, and dogs in 2005.

“And what about primates? If the original fear was human cloning, it should be possible to clone other primate species first. The truth is that the first successful cloning of primates didn’t happen until February 2018, exactly 21 years after Dolly’s birth. A team of Chinese researchers, led by Qiang Sun from the Chinese Academy of Sciences in Shanghai, described the cloning of crab-eating macaques (Macaca fascicularis) in the journal Cell. The significance of that article was the efficiency of the process, around 1.5%, surprisingly low and not far from what was obtained in the original cloning of Dolly and in most cloned species, once again emphasizing the technical difficulties of the somatic cell nuclear transfer (SCNT) process, which is the appropriate term for cloning. This poor efficiency confirmed the obvious: not only was human cloning unnecessary and debatable, but if attempted, it would be extraordinarily difficult and ethically unjustifiable.

“Now, almost six years later, the same team of Chinese researchers, again led by Qiang Sun along with Zhen Liu, reports in the journal Nature Communications the cloning of another primate species, the Rhesus monkey (Macaca mulatta), after multiple previous failed attempts. Success was achieved by combining the treatment of cloned embryos with Trichostatin A (a histone deacetylase inhibitor) and Kdm4d (a histone demethylase), both already used in the previous cloning of crab-eating macaques and aimed at altering the epigenetic state of cloned embryos, with a sophisticated method of trophoblast replacement, the cells surrounding the inner cellular mass in the blastocyst that will later give rise to the placenta. Again, the efficiency of the process is similar, even lower: one surviving cloned animal out of 113 initial embryos, less than 1%.

“Both the cloning of crab-eating macaques and Rhesus monkeys demonstrate two things. First, it is possible to clone primates. And second, no less important, it is extremely difficult to succeed with these experiments, with such low efficiencies, once again ruling out human cloning. The authors suggest that this technique should complement the use of both primate species in biomedical research. As a derivative of their new cloning method, they mention that trophoblast replacement could have potential as a new assisted reproduction technique in cases where human embryos show deficiencies in trophoblast development.

“Finally, it is worth noting that these experiments could not have been conducted in Europe, as the European Union’s legislation on animal experimentation prohibits the use of non-human primates unless the experiment is aimed at investigating a serious, life-threatening disease affecting humans or the primate species itself, which is not the case in this experiment.”

‘Reprogramming mechanism dissection and trophoblast replacement application in monkey somatic cell nuclear transfer’ by Zhaodi Liao et al. was published in Nature Communications at 16:00 UK time on Tuesday 16 January 2024.

DOI: 10.1038/s41467-023-43985-7

Declared interests

No reply to the request for DOIs was received.