It is still very difficult to carry out the “virgin fertilization” procedure on a large scale in practice – it is impossible to edit with equal efficiency all the regions in the genome responsible for suppressing part of the genome, that is, for genomic imprinting. There is a high probability that at least one of them will not be “corrected” – and this immediately reduces the viability of the resulting new organism.
Parthenogenesis is same-sex reproduction or “virgin reproduction” when female reproductive cells (eggs) develop in an adult body without fertilization. Parthenogenesis is characteristic of a small number of multicellular organisms, for example, snails, crustaceans, cockroaches, spiders, aphids, ants, termites, some types of lizards, amphibians, fish, birds, including some chickens. Parthenogenesis has not been observed in mammals. The main biological advantage of parthenogenesis is the acceleration of the rate of reproduction of the species, since all individuals of such species are capable of leaving offspring.
Mammals do not appear to be able to reproduce parthenogenetically, that is, to produce offspring from a single germ cell. Even in laboratory conditions, no one has yet obtained such results. This is prevented by genomic imprinting – a process during which the sperm and egg attach epigenetic marks to their DNA, as a result of which some genes do not work in the chromosomes that the new organism receives from its father and mother.
This time, according to tradition, the subjects in the experiment were mice, the journal Proceedings of the National Academy of Sciences will publish. The authors of the work took growing oocytes, that is, egg precursors, from hybrid females. And they launched “genetic scissors” based on CRISPR/Cas9 into them. They used a modified system in which Cas9 does not cut DNA, but demethylates it, that is, removes epigenetic marks from it.
For the first time, Shanghai scientists managed to carry out true parthenogenesis, without the use of other reproductive donor cells. True, they noted that the efficiency of the technology is still very low: in order to get two viable mice, they had to implant 155 embryos into the females at the stage of 3.5 days of development.