British molecular biologists have created a full-fledged embryo for the first time, bypassing the fertilization phase of the egg and its fusion with the sperm, which will simplify the cloning process in the future, according to an article published in the journal Nature Communications.
“Our work casts doubt on the almost 150-year-old dogma that only the fertilization of an egg with a sperm cell leads to the formation of a full-fledged embryo and the birth of healthy offspring. Until then, we believed that only an egg can 'reprogram' sperm so that the normal development of the embryo begins, said Tony Perry from the University of Bath (UK).
Some living creatures, for example, lizards, chickens, fish or many insects, are capable of parthenogenesis - self-fertilization, in which two eggs merge with each other, forming an embryo, or the female reproductive cell spontaneously begins to develop, despite the "half" set of chromosomes … For mammals, this method of reproduction is completely uncharacteristic, and there is not a single animal species that would be capable of this even in theory.
According to Perry, attempts to artificially induce parthenogenesis were carried out in the early 2000s, when scientists tried to "cheat" the egg by chemical means and force it to "start" the embryo development program by adding a solution of strontium chloride to the nutrient medium. It turned out that such a trick is feasible, but such "half" embryos, which scientists call parthenogenotes, inevitably die after several cycles of division.
For this reason, scientists believed that eggs have unique properties and mechanisms that allow them to start the process of birth of a new life and the fusion of paternal and maternal "halves" of DNA, their purification from the so-called epigenetic marks and other procedures that are critical for the development of the embryo.
It turned out that this is not the case. Experimenting with such bodies, the authors of the article found that they can "reprogram" spermatozoa and even the preparation of male germ cells, making them suitable for fusion with the "half" DNA of parthenogenotes and continuing development already in the form of a full-fledged embryo. According to scientists, such a process was completed successfully and led to the birth of healthy mice in 24% of cases, which is a very high chance of success with the cloning procedure.
Mice born in a similar way did not differ from the "normal" offspring of rodents and had a similar mass, size, intelligence, just as often suffered from those diseases that affect mice and could reproduce successfully, giving healthy offspring when crossed with each other or with "ordinary »Individuals of the opposite sex.
Their only difference from "natural" mice was how often their genes were read - parthenogenesis, apparently, does not lead to the purification of epigenetic marks on DNA obtained from the "father", which changes the readability of some regions of their genome.
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The success of this procedure, as noted by Perry and his colleagues, paves the way for the creation of technologies for "self-fertilization" of a person, which are of interest to physicians for the reason that they allow obtaining "pure" lines of embryonic stem cells, without causing ethical problems associated with the destruction viable embryos. In addition, parthenogenesis can help scientists uncover the genetic roots of rare diseases faster by creating animals with a genome that consists of identical halves.
