A healthy monkey was successfully cloned by a team of Chinese researchers and survived for more than 2 years. A company report is published in the journal 'Nature Communications'. The cloned specimen was a male rhesus macaque and the results were obtained after providing the photocopy embryo with a healthy placenta.
Qiang Sun, Zhen Liu and colleagues from the Chinese Academy of Sciences in Shanghai and the University of Chinese Academy of Sciences in Beijing performed a comparative analysis between epigenetic datasets of blastocyst-stage monkey embryos derived from fertilization in in vitro (IVF) and those cloned by somatic cell nuclear transfer.
They identified anomalies in the way genetic information can be accessed and read from the developing cloned embryo and its placenta, and anomalies in the size and shape of the placentas of cloned monkeys that were developing in surrogate mothers.
To address these issues, the authors developed a method to provide the developing clone embryo with a healthy placenta. Using this approach, Scientists managed to get the healthy male rhesus monkey to survive for more than two yearsprotagonist of the study whose first author is Zhaodi Liao, of the Center for Excellence in Brain Science and Intelligence Technology.
The illustrated findings advance understanding of the mechanisms of primate reproductive cloning and could help improve its efficiency, the authors suggest. The body's somatic cells, such as skin cells, contain the genetic information about how an organism is built, but they cannot give rise to new organisms. Somatic cell nuclear transfer technology has already successfully led to the cloning of various mammalian species, including the famous Dolly sheep, progenitor of cloned mammals, and cynomolgus monkeys. However, experts reason, the cloning efficiency of most mammalian species remains extremely low, with high fetal and neonatal mortality rates.
For the rhesus monkey, one study reported a successful somatic cell clone, but the monkey did not survive after birth. Now the Chinese team's feat takes a step forward. Although only one healthy rhesus monkey clone based on this method has been reported so far, the results could prove to be a promising strategy for primate cloning in the future, the experts conclude.
Because it's an important step
The cloning of a monkey by a group of Chinese researchers “clarifies a biological aspect of the development of embryos that was elusive until today. The development of cloned primates had a very low success rate, around 20%, on the contrary, for example of cattle for which it is much higher. Many have wondered if there was a problem linked to the phenomenon of genomic imprinting, one of the mechanisms by which genes are regulated. The novelty of this new cloning is having discovered the imprinting defect in basis of reproduction and having analyzed the biological problem that gives rise to it I believe that the work can open up interesting scenarios to overcome infertility problems in couples“, Giuseppe Novelli, professor of medical genetics at the Tor Vergata University of Rome, tells Adnkronos Salute.
A very complex process occurs in genomic imprinting. “We receive a regulation of the genes – explains Novelli – like an orchestra in which each instrument plays differently. If the genes all 'sounded' the same way, there would only be great chaos and this also happens in biology. In this regulation some genes turn off and others turn on, a process that is important in mammals and occurs during fertilization between male and female. When cloning is done, one does not start from gametes, but from a nucleus that is transferred. But one of the defects of cloning is the alteration of imprinting, where the various 'actors' of this mechanism can have problems.”
“The new idea developed in this Chinese study – continues the geneticist – is to have analyzed the trophoblast, the cellular tissue that serves to nourish the embryo, an early placenta. Some failures of medically assisted procreation (Pma) procedures occur precisely in this phase. The scientists saw that the main alteration of imprinting occurs precisely at the level of the trophoblast and decided to intervene here, setting up cloning and traditional fertilization in parallel. From the first they took the embryo and 'They transferred it into a blastocyst and then did a trophoblast transplant, the latter obtained with fertilization between gametes.” Novelli then points out that this study “will not lead to any serial human cloning, but simply demonstrates the role of the early placenta in the development of some defects in the early stages”.
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