Two healthy monkeys have been successfully cloned by researchers in China. Two long-tailed macaque monkeys were successfully cloned using the cloning method that produced Dolly the sheep 22 years ago. The monkeys were born at a lab in Shanghai ten days apart, in November and December. The cloning was reported in the scientific journal Cell.
The cloned monkeys were named Zhong Zhong and Hua Hua. They are the first primates to be cloned using a non-embryonic cell. The scientists reported they are in good health and continue to grow normally. The researchers said they expect more macaque clones to be born over the coming months.
One of the paper’s authors, Muming Poo, said in a news conference in China that the work was done to produce primates that could be models to understand human medical conditions. They could also be used to test new drugs before clinical use. Genetically identical animals are useful in research because genetic variability can complicate experiments. Poo directs the Institute of Neuroscience at the Chinese Academy of Sciences Center for Excellence in Brain Science and Intelligence Technology.
Researchers have been trying to clone primates since Dolly’s birth in 1996, but until now no primate clones have been reported. The cloning of primates was long thought to be fundamentally more difficult than cloning other mammals like horses, dogs, and sheep. Since 1996, scientists have successfully used the same method to clone more than 20 other species. Similar work in primates had always failed.
The Chinese team originally created 79 long-tailed macaque monkey embryos which they implanted in surrogate long-tailed macaque monkey mothers. Only six of those became pregnant and only Zhong Zhong and Hua Hua survived. The technique worked only when nuclei were transferred from fetal cells, rather than adult ones. In all, 127 eggs were needed to produce two live macaque births.
The team created the embryos using cells from fetal connective tissue. It was achieved through a process called somatic cell nuclear transfer (SCNT). The process involves transferring the nucleus of a cell, which includes its DNA, into an egg which has had its nucleus removed. The team succeeded by using modulators to switch certain genes that were inhibiting embryo development on or off.
The success brings science another step closer to being able to clone humans. Poo said in a conference call, “Humans are primates. So (for) the cloning of primate species, including humans, the technical barrier is now broken.” Poo also said the team has no intention of using their techniques to clone humans.