A team of Chinese scientists has announced a new milestone to the world: they have successfully cloned primates using somatic cell nuclear transfer, the same cloning technique that the first cloned mammal , the endearing Dolly the sheep, gave us in 1996.
Their names are Zhong Zhong and Hua Hua and, yes, they are clones of the same fetal macaque fibroblasts, not an adult cell. They were born 8 and 6 weeks ago respectively. They are two genetically identical long-tailed macaques, born at the Institute of Neuroscience of the Chinese Academy of Sciences in Shanghai.
However, they are not the first primates to be cloned, that honor goes to Tetra , a rhesus monkey cloned in 1999 in Oregon using the embryo division method. This cloning technique is easier to achieve, but has limitations that are not supported by somatic cell nuclear transfer.
Scientists were able to modify the advanced technique of somatic cell nuclear transfer to finally work in primates , but the road was not easy. “We tried several different methods, but only one worked. There were many mistakes before we found a way to successfully clone a monkey,” said Qiang Sun, leader of the work.
Embryo division is exactly what it sounds like, and it’s the same process that produces identical twins in the womb, albeit artificially. It is a technique that is often used for assisted reproduction in farm livestock. However, at most, it is only possible to produce four genetically identical siblings, quadruplets.
Rather, to create a clone using somatic cell nuclear transfer, the nucleus of an egg must be replaced with the nucleus of a somatic cell , which contains DNA from another individual. They found that preventing epigenetic changes in DNA – chemical modifications that affect the way certain sequences are expressed – increased the chances that other cloned embryos would survive.
It was a big step, but there were still problems to be solved. While the researchers succeeded in bringing the fetuses to term using cells from adult donors in the eggs, the baby monkeys only survived for a short period of time after birth.
Debugging the technique
Finally, they improved their success by using cells taken from fetal tissue. Zhong Zhong and Hua Hua were cloned using the same fetal fibroblasts, cells taken from the connective tissue of a macaque fetus.
“There are many questions about primate biology that can be studied with this additional model,” Sun said.
“You can produce cloned monkeys with the same genetic background, except for the gene that you manipulated. This will generate real models not only for gene-based brain diseases, but also for cancer, the immune system or metabolic disorders, and will allow us to test the efficacy of drugs for these conditions before clinical use. “
The experimental use of primates is controversial in many parts of the world. It is regulated in the EU, where it is only allowed if no other methods are available, and it is prohibited to varying degrees in some regions. However, due to their genetic proximity to humans, their intelligence, and their social dynamics, non-human primates are considered vital for biomedical research.
Scientists will continue to closely evaluate Zhong Zhong and Hua Hua in their mental and physical development. At the moment, both are thriving and growing at a healthy rate and more macaque clones are expected to be born in the coming months.
Referencia: Cloning of Macaque Monkeys by Somatic Cell Nuclear Transfer. Zhen Liu, Yijun Cai, Yan Wang, Yanhong Nie, Chenchen Zhang, Yuting Xu, Xiaotong Zhang, Yong Lu, Zhanyang Wang, Muming Poo. Cell Press 2018 DOI: http:/ /dx.doi.org/10.1016/j.cell.2018.01.020
Crédito imagen: Qiang Sun and Mu-ming Poo/Chinese Academy of Sciences
