Chinese biologists first got healthymonkey babies that appeared due to the method of transferring a nucleus from a somatic cell to an egg without its own nucleus. The born Javanese macaque cubs are complete genetic copies of the cells of the connective tissue of a monkey donor, from which nuclei were taken for cloning. Recall that the first animal cloned in this way was the famous sheep Dolly, which was born in 1996. Chinese geneticists describe the results of their work in the journal Cell.
“Creating a monkey cloning technique gives usa lot of new features. Now we can grow primates with an absolutely identical set of genes, with the exception of one piece of DNA whose structure we have changed. This will help not only to reveal the essence of many genetic diseases, but also to find new methods of combating cancer and immune disorders, ”says Qiang Song, director of the Center for the Study of Primates at the Institute of Neurophysiology of the KAN in Shanghai.
The first cloned animal on Earth, a sheepDolly was the “product” of three mothers, one of whom left her genetic material, the second gave the first egg, and the third bore it after successfully transferring the DNA of the first parent to the reproductive cell of the second.
Dolly’s birth ushered in a new era in biology andgenetics - now scientists have the opportunity to create "clean" lines of experimental animals with absolutely identical DNA, as well as to resurrect extinct species of living things. Initially, scientists feared that the cloning procedure leads to accelerated aging of the body and rarely succeeds, but in recent years they have been able to show that this is not the case and increase the chances of success to 70-80%.
According to Song, despite all these successes, to date, no scientific team has been able to clone a macaque or any other monkey in the same way that Dolly did.
“We tried to use several differentkernel transfer techniques, and only one of them worked. We had to face a huge number of mistakes and failures before we discovered the correct method for cloning monkeys, ”Song continues.
The key to solving this problem, as notedThe Chinese biologist began to accelerate the process of transferring the nucleus from the “normal” donor monkey cell to an empty egg, which significantly reduced the likelihood that its further development would go the wrong way. In addition, scientists developed a special “cocktail” of enzymes and RNA molecules that protected the protein coat of DNA from damage and caused the egg to divide after a new nucleus was introduced into it.
Primary culture of donor fibroblasts (A), the procedure for extracting the nucleus from the egg cell (B, C) and the procedure for fusion of the egg with the nucleus of fibroblast (D-F)
The fruit of all efforts were two newbornsJavanese macaques (Macaca fascicularis), born to a surrogate mother 8 and 6 months ago, have exactly the same DNA. The first was named Zhong Zhong, and the second - Hua Hua.
Zhong Zhong (left) and Hua Hua (right)
Similar nicknames, as scientists note, area kind of pun - the expression of Zhonghua means “Chinese people” in the language of the Middle Kingdom. Both monkeys have no health problems and grow and develop in the same way as other monkeys at this age.
According to Chinese researchers, similarthe cloning procedure is completed successfully in every third case, if the DNA donor is connective tissue cells (fibroblasts), prepared in a special way. This indicator, according to Song, can be made even higher in the future by further optimizing the kernel transfer procedure.
Scientists recognize that in past sciencemanaged to create a copy of the monkey, but in the strictest sense it was not a clone. Biologists simply divided the embryo into several parts in the first phases of its development, which led to the birth of not one, but two monkeys. In this way, no more than four individuals can be “cloned” at a time, which greatly limits the scientific usefulness of this technique compared to the ideas of Sun and his colleagues.
Cloning of animals, scientists are engaged in the firstthe turn is in order to better understand the processes of embryo development, however, such experiments have some applied benefits. For example, cloning monkeys would help create models of genetically determined human diseases that are needed to study the mechanisms of development of these diseases and test drugs. Such models are used in mice, but monkeys are genetically and physiologically much closer to humans, so such studies give more adequate results.
Fibroblasts of the fetus, which Chinese scientistsused for cloning, lend themselves well to genetic modifications, including using the CRISPR / Cas9 system. Therefore, the successful cloning of macaques precisely from these cells means that the creation of genetically modified monkeys is just around the corner.
Opponents of the cloning procedure claim thatanimals that are born in this way may contain latent developmental defects and are therefore less viable. For example, Dolly the sheep was notable for poor health, suffered from arthritis and lived for only six years. However, recently, scientists found out that Dolly did not have any particular predisposition to diseases, and she was ill, most likely, because of her content indoors and low mobility.