MEET ZHONG ZHONG AND HUA HUA – THE WORLD’S FIRST MONKEYS CLONED THE SAME WAY AS DOLLY
Two genetically identical long-tailed macaque clones have been successfully bred by Chinese researchers
A pair of primate clones bred using somatic cell nuclear transfer (SCNT), the technique used to create Dolly the sheep more than 20 years ago, have been born at the Chinese Academy of Sciences in Shanghai.
The newborns are just several weeks old and have been named Zhong Zhong and Hua Hua after the Chinese adjective ‘zhonghua’, which means Chinese nation or people. They are currently being bottle-fed and are developing normally compared to other monkeys their age.
In SCNT, the nucleus is removed from an egg cell and is replaced with a different nucleus from another cell. The egg cell then merges with the implanted nucleus and develops into a clone of whatever it was that donated the nucleus.
Previously, in sheep, mice and cows, adult donor cells have been used to create healthy clones. However, adult primate cells proved resistant to the technique. The Shanghai team overcame this by using donor cells taken from a macaque foetus.
While Zhong Zhong and Hua Hua are the first primates to be cloned using this technique, primates have been cloned in the past. In 1999, a rhesus macaque called Tetra became the first primate to be cloned, though this was achieved using a simpler method called embryo splitting. Here, the cells in the embryo are split after reaching the eight-cell stage to create four identical two-cell embryos in a manner similar to naturally occurring twins.
The breakthrough will make it possible to breed genetically uniform monkeys. This will enable researchers to study primates in unprecedented detail, as well as help with the development of drugs and therapies for use in humans. “There are a lot of questions about primate biology that can be studied by having this additional model,” said Prof Qiang Sun. “This will generate real models, not just for genetically based brain diseases, but also cancer, immune or metabolic disorders and allow us to test the efficacy of the drugs for these conditions before clinical use.”
The researchers are eager to point out that they are following strict guidelines for animal research set by the US National Institutes of Health, and accept that the scientific community should debate acceptable laboratory practices concerning the cloning of non-human primates. “We are very aware that future research using non-human primates anywhere in the world depends on scientists following very strict ethical standards,” explained co-author Prof Muming Poo.
They now plan to continue improving the technique and expect more macaque clones to be born over the coming months.
Ultrasound scans of surrogate uteruses from the SCNT process. The uterus on the left contains no foetus, but the one on the right has been successfully impregnated and the foetus can be seen