Ever since Dolly the Sheep showed that most of the problems with cloning large mammals had been, in large part, resolved, we’ve been walking closer to the day when a human being could be cloned. Now Nature is reporting that scientists at the Chinese Academy of Sciences have succeed in cloning a pair of long-tailed macaques. This achievement indicates that previous difficulties in cloning primates using the same somatic cell nuclear transfer technique used to clone Dolly and thousands of sheep, pigs, cattle and other animals since. It also means that cloning humans is not even one technical leap away.
Previous efforts to clone primates often successfully created embryos, but damage to the nuclear material during extraction affected development and the efforts ended in failure. Even this successful effort was not without a large number of failures.
Using fetal cells, they created 109 cloned embryos, and implanted nearly three-quarters of them into 21 surrogate monkeys. This resulted in six pregnancies. Two long-tailed macaques (Macaca fascicularis) survived birth: Zhong Zhong, now eight weeks old, and Hua Hua, six weeks. Poo says that the pair seem healthy so far. The institute is now awaiting the birth of another six clones.
Similar difficulties occurred in using the Somatic Cell Nuclear Transfer technique in other species, but subsequent efforts have greatly improved the viability of cloned embryos. Similar improvements can be expected with primates.
But the achievement is also likely to raise some concerns among scientists and the public that the technique might be used to create cloned humans. “Technically, there is no barrier to human cloning,” says ION director Mu-Ming Poo, who is a co-author of the study.
Which means that, just as it has been for several years now, the primary issues around cloning humans are ones that need to be solved through ethics, not laboratory technique.
The Chinese team hopes to use the cloned animals to improve research.
Researchers hope to use this revised technique to develop populations of genetically identical primates to provide improved animal models of human disorders, such as cancer. The technology, described in Cell1 on 24 January, could also be combined with gene-editing tools such as CRISPR–Cas9 to create genetically engineered primate-brain models of human disorders, including Parkinson’s disease.
The macaques cloned by the Chinese team are not technically the first cloned primates. A rhesus macaque named “Tetra” was created in 1999 through a technique called “embryo splitting” — essentially the forced creation of an identical twin.
The technique used with Dolly and the monkeys cloned in China was first used with mice in 1986, with sheep in 1996, pigs in 2000, goats in 2001, cattle in 2001, cats in 2001, and dogs in 2005. It’s become reliable enough to be used for reproducing valuable animals for commercial purposes. In 2001, the technique was used to clone an endangered Gaur. In 2009, the extinct Pyrenean ibex was cloned back into existence using tissue from the last living ibex, which had died a decade earlier. However, the resulting clone had lung issues and died within minutes of birth.
Multiple reports of human cloning have appeared, but none of them are believed to represent anything more than fiction.