Chinese scientists have achieved a major breakthrough by successfully cloning the first healthy rhesus monkey using somatic cell nuclear transfer (SCNT), the same technique used to clone Dolly the sheep in 1996. The monkey, named “Retro”, was born in late 2021 and is still alive and healthy after over two years, significantly longer than any other primate cloned using SCNT.
Background on Cloning and Previous Primate Cloning Attempts
Cloning creates an identical genetic copy of an organism by transferring the nucleus from a body cell into an egg cell that has had its own nucleus removed. The first mammals cloned from adult cells using SCNT were sheep by scientists in Scotland in 1996, resulting in Dolly, who lived for six years.
Since then, SCNT has been used to clone over 20 different mammalian species, including cows, dogs, horses and pigs. However, primate cloning has proven extremely difficult. Before Retro, cloned primates typically lived only a few days after birth due to abnormal development.
The first primate cloned using SCNT was Tetra the rhesus monkey in 1999, but she died soon after birth. In 2018, Chinese scientists created two cloned macaques named Zhong Zhong and Hua Hua using SCNT, but they only lived a few weeks.
| Year | Cloned Primate | Lifespan |
|---|---|---|
| 1999 | Tetra (rhesus monkey) | Died soon after birth |
| 2018 | Zhong Zhong and Hua Hua (macaques) | Lived a few weeks |
Retro is the first primate clone using SCNT to survive past early infancy, a major milestone.
Details on the Cloning Process Behind Retro
The research team that created Retro was led by Dr. Zhen Liu at the Yunnan Key Laboratory of Primate Biomedical Research in China. They published their results in the journal National Science Review.
To create Retro, the scientists used fetal fibroblasts taken from a male rhesus monkey fetus as the DNA donor. After removing the nucleus from a female rhesus monkey egg cell, they injected the fetal fibroblast nucleus in a delicate procedure requiring sophisticated equipment.
The key innovation enabling Retro’s successful cloning was the addition of caffeine and trichostatin A during embryo development, which helped improve embryo quality. The drug cocktail influenced epigenetic modifications, enhancing reprogramming of the donor genome after nuclear transfer into the egg cell.
Using over 100 rhesus monkey egg cells, the scientists generated six embryos, one of which was carried to term by a surrogate mother monkey. Retro was born in late 2021 via caesarean section and is still healthy today in 2024. Compared to typically short-lived primate clones, Retro exhibits normal anatomy, physiology and cerebrum development according to full-body MRI scans. Genetic analyses confirmed Retro was an identical clone of the DNA donor.
“We tried several different methods and conditions over the past five years before we finally succeeded,” said Dr. Liu. “Our method could improve primate cloning efficiency and might be useful for producing genetically uniform populations of monkeys for biomedical research.”
Potential Applications and Ethical Issues with Primate Cloning
Now that primate cloning is possible, it opens up several potential applications while raising ethical concerns.
Rhesus monkeys share over 90% of human genes, meaning cloned monkeys could act as ideal animal models for testing drugs and modeling diseases to benefit human health. Producing genetically uniform cloned monkeys could also benefit organ transplantation research.
However, many experts argue human reproductive cloning should remain banned. Since the technique used to produce Retro could theoretically clone humans, it reopens debates on whether human cloning laws need revising. Most countries ban human cloning due to ethical issues like difficulty ensuring clone health and objections around “playing God”.
“There is no medical necessity or ethical justification to clone human beings,” stressed Dr. Robert Klitzman, director of the bioethics program at Columbia University. “We already have other ways of doing research to develop cures for diseases.”
Reaction from Scientific Community and Future Outlook
The cloning of Retro made headlines worldwide and sparked debate within the scientific community. Many scientists hailed it as an exciting development for genetic and medical research. Others argued we still know too little about primate cloning to justify further experiments.
“This research opens up both enormous scientific possibilities and ethical uncertainty,” said geneticist Dr. George Daley from Harvard University. “We still have much to learn about primate embryology and cloning.”
Dr. Shoukhrat Mitalipov, who led the team that created Zhong Zhong and Hua Hua, believes perfecting primate cloning will still take more innovation. “While a remarkable advance, multiple steps remain before clinical applications are feasible,” he noted.
Looking ahead, further work is still needed to better understand factors causing clone abnormalities and improve success rates. But with rapid advances in cloning technology as shown by Retro, it appears only a matter of time before primate cloning becomes routine. The big question now is where to draw the line ethically between animal cloning benefiting human welfare versus human cloning crossing the Rubicon.
To err is human, but AI does it too. Whilst factual data is used in the production of these articles, the content is written entirely by AI. Double check any facts you intend to rely on with another source.
