Two moms: Like same-sex pair of mice have offspring
Dmitry Kurkin
The Chinese team of scientists was able to achieve appearance of healthy offspring in same-sex pair of mice. An experiment to change the genetic code was conducted with the participation of a pair of males and a pair of females. Mice that had only paternal genes died two days after birth, while mice born with the DNA of two mothers feel good and do not look any different from ordinary individuals of their own species — they even managed to give offspring.
This event is called a breakthrough in genetic engineering: until now, mammals were able to reproduce only with the participation of genetic material from males and females - this combination was obligatory. Representatives of other classes of animals - including fish, reptiles and amphibians - can produce offspring without the participation of another partner, but in the mammalian world there was an unshakable rule of imprinting.
The biological imprinting phenomenon has not been fully investigated, but on the whole it is considered to be a kind of competition between two DNA, maternal and paternal, for whose genes will receive the offspring. As a result of this process, a part of the genetic code of the offspring inherits from females, another part - from males, and unused genes in each of the chains are "turned off" by natural chemical "silencers". In the case of mixing genes of same-sex parents, it usually fails due to the fact that the same DNA strands remain either “turned on” or simultaneously “turned off”. This leads to genetic abnormalities already at the stage of fetal development and, most often, to miscarriage.
Is it possible to deliberately edit the DNA so that the genes "turn on" and "turn off" in the right way and make up a full-fledged combination that will ensure the birth of healthy offspring? This question was asked by Chinese researchers - and received a somewhat positive answer to it. First, they needed to identify those areas of DNA that are responsible for imprinting, and remove them so as not to damage other vital areas. For this jewelry operation, CRISPR / Cas9 technology was applied, allowing editing of genetic chains. In both experiments, scientists created haploid cells (containing half a set of chromosomes) of mouse stem cells, some of which were turned into “pseudosperm” by means of genetic editing, and others into imitation of eggs.
In the case of male mice, editing the haploid cell turned out to be much more difficult: for this, seven genetic areas had to be removed instead of three (as in the case of a pair of females), and even this was not enough, judging by the fact that the experiment on the males ended in failure. "The rapid death of the offspring [of two males] indicates that unknown barriers still remain in the path of reproduction and development," said one of the authors of the study, Dr. Hu Baoyang. "Successful reproduction of offspring from two males happens very rarely, we only see it in certain types of fish and only in the laboratory. "
Although mice born from two mothers look healthy, genetic abnormalities in both them and their offspring may appear much later.
The experiment with the DNA of two females turned out to be much more successful: out of two hundred and ten of the obtained embryos, twenty-nine were born alive, seven of which, in turn, were able to give offspring (already without the intervention of geneticists, in the usual way for mice).
Does this mean that reproductive technologies are on the verge of allowing same-sex parents to have one hundred percent "their" (from a biological point of view) children? Do not rush to conclusions. Chinese scientists have done outstanding work, but they don’t set themselves the task of moving from mice to humans. Moreover, as Dr. Zhang Yi from Harvard Medical School notes, such a transition is "at least ten times more difficult."
This view is shared by many commentators from the scientific world. They agree that the development of genetic editing for human genes will take much more time and in the short term does not look real. For ethical reasons as well: although mice born from two mothers look healthy, genetic abnormalities in them and in their offspring may appear much later. In the case of people, scientists simply cannot afford such a risk. “In such things, the security issue is important to me,” says lawyer Sonya Souter, professor of bioethics at George Washington University.
“Creating a human child in this way looks like an unthinkable task,” says Christophe Galische, a scientist at the Francis Crick Institute in London, while noting that “the authors [of the research] made an extremely important step in studying why mammals can only reproduce sexually.” .
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