Last week, it was announced that Chinese scientists accomplished a genetic landmark: the cloning of two monkeys. The two identical long-tailed macaques, named Zhong Zhong and Hua Hua, were born two weeks apart and cloned from the connective tissue cells of monkey fetuses, according to the study published in the scientific journal Cell.
What makes the cloning of these two female monkeys so noteworthy? Zhong Zhong and Hua Hua are the first primates cloned using somatic cell nuclear transfer – the technique used to clone Dolly the sheepmore than 20 years ago.
Utilizing the SCNT method, scientists removed a nucleus from a somatic cell (connective tissue cell) of an aborted monkey fetus and inserted it into an egg cell which had its DNA-embedded nucleus previously removed. Researchers then applied two enzymes to the egg containing a newly implanted nucleus, returning the cell to an early embryonic stage.
That egg was then implanted into a surrogate monkey mother.
This process was repeated by scientists numerous times – with a fairly low success rate: nearly 80 embryos were implanted into 21 surrogate monkeys, which resulted in six pregnancies and ultimately, two live births: Zhong Zhong and Hua Hua.
“The nucleus contains the majority of the DNA,” said Dr. Elizabeth McNally, a cardiologist, geneticist and the director of Northwestern’s Center for Genetic Medicine. “They took an entire nucleus from a previously existing monkey and used that to replicate the monkey, so it truly is cloning – they created an exact duplicate of that monkey.”
Since Dolly earned the distinction as the first mammal cloned via SCNT in 1996, more than 20 mammals – from cattle to cats to mice – have been cloned this way, but no other species that so closely mirrors human genetic makeup.
“Macaque monkeys and humans share a lot of the same genomes, so it’s not that far off from cloning a human,” said McNally. “A lot of the reproductive aspects of monkeys, particularly the macaques, turns up in humans, as well.”
McNally said she guessed with “fairly modest modulations, you could really get this to work in humans.”
The scientists behind the macaque cloning experiment said their work could potentially produce cloned research monkeys with specific genetic defects used to test various treatments in the biomedical industry.
McNally said genetically identical animals could be valuable in research environments, but it depends on which species.
“If you could make animals that were completely identical to each other, then you could do experiments with a lot more replicability because the animals are all the same,” McNally said. “I don’t know how much that will happen with monkeys because in general, there’s a lot less interest in doing primate-based research, certainly in the United States.”
McNally joins “Chicago Tonight” to discuss this scientific breakthrough and its implications.