By Kenneth Manson
Meet Zhong Zhong and Hua Hua, the first primates to ever be cloned on record. They are identical crab-eating macaques cloned using the same technique that claimed the first ever successful mammalian clone, Dolly the sheep. They were named after the after the two characters that make up the China’s name in Chinese, Zhonghua (中华). The two of them are the first births of the six pregnancies from the placement of 21 cloned ovas, and are expected to be joined by more of the clones soon. They were born at the Institute of Neuroscience of the Chinese Academy of Sciences in Shanghai.
Previously, besides Dolly herself, 23 mammalian species including cattle, cats, dogs and horses were cloned using the somatic cell nuclear transfer technique or SCNT. However, cloning primates eluded success until now. The failure in earlier attempts are blamed on epigenetics, a branch of biology that deals with heritable traits that affect gene function and expression and may even persist through generations of progeny despite not modifying the underlying DNA sequences. SCNT works by removing the nucleus of an egg cell and essentially transplanting a nucleus with the DNA from the cell of the individual whose clone is desired. Put simply, external factors within the egg that controlled gene expression within the cell prevented it from dividing into a successful clone, a problem remedied by the Chinese researchers using a couple of enzymes to eliminate the interferences.
While the birth and life of Zhong Zhong and Hua Hua aren’t technically the first mammalian “clones”, the earlier specimen called Tetra, a rhesus macaque, was the result of the embryo splitting technique, which is artificial reproduction of the same natural process that results in identical twins, that is artificial twinning in effect.
Though the breakthrough can bee seen as an enabler to studying more diseases like the eponymous lab rats, concerns are already abound that this development brings us closer to cloning humans, since homo sapiens are also scientifically classified as primates. The director of the Institute of Neuroscience, Muming Poo, emphasizes on using the genetically-identical monkeys to advance the research of diseases such as Alzheimer’s, Huntington’s and Parkinson’s, while crab-eating macaques are already an established model organism for researching atherosclerosis. At the same time, he vigorously denied using the successful momentum on anything remotely human.
Beyond cloning, the SCNT itself is championed for its potential of “therapeutic cloning” to advance regenerative medicine to clone entire tissues or even organs as a method to replace or repair damage. Its viability in that frond are still subject to debate, however.