Chinese scientists for first time have successfully cloned two identical long-tailed macaques (monkeys), named Zhong Zhong and Hua Hua using same technique that produced Dolly sheep two decades ago. This development makes them world’s first primates – the order of mammals that includes monkeys, apes and humans – to be cloned from non-embryonic cell.
These two identical long-tailed macaques were cloned using process called somatic cell nuclear transfer (SCNT), which involves transferring the nucleus of cell, which includes its DNA, into egg whose nucleus is removed.
Since cloned Dolly sheep was born in Scotland in 1996 using SCNT, scientists have successfully used this technique to clone more than 20 other species, including cows, pigs, dogs, rabbits, rats and mice. Similar work in primates earlier, had always failed, leading some scientists to wonder if primates were resistant.
Chinese Scientists were successful to clone macaques using modulators to switch on or off certain genes that were inhibiting embryo development. Their technique worked only when nuclei were transferred from foetal cells, rather than adult ones, as was the case with Dolly. In all, it took 127 eggs to produce two live macaque births.
Genetically identical animals are useful in research because confounding factors caused by genetic variability in non-cloned animals can complicate experiments. This development breaks technical barrier for the cloning of primate species, including humans. It will make possible to study diseases in populations of genetically uniform monkey and test new drugs for a range of diseases before clinical use.
The research underscores important role at the cutting-edge of biosciences, where scientists have at times pushed ethical boundaries but calls for debate on what should or should not be acceptable practice in primate cloning.
Somatic cell nuclear transfer (SCNT)
SCNT is a laboratory technique for creating an ovum with donor nucleus. In it, nucleus containing the organism’s DNA of somatic cell (a body cell other than sperm or egg cell) is removed and rest of cell discarded. The nucleus of somatic cell is then inserted into enucleated egg cell which reprograms somatic cell nucleus by the host cell. The egg, now containing nucleus of somatic cell, is stimulated with a shock and will begin to divide forming blastocyst (an early stage embryo with about 100 cells) with almost identical DNA to original organism. It can be used in embryonic stem cell research, regenerative medicine i.e. “therapeutic cloning.” It can also be used as first step in process of reproductive cloning.