In the mouse family, they asked for the dad, then another dad and finally the baby mouse.
But of mother, it was not question of it.
Katsuhiko Hayashi, a famous Japanese developmental biologist, announced that he succeeded in giving birth to healthy baby mice using only male stem cells on Wednesday March 8 at the third International Summit on Human Genome Editing. in London.
The work of his team has not yet been published, but it has submitted the article describing the feat to the journal Nature, said the Japanese researcher.
A father's egg
If this scientific breakthrough were to be confirmed by the famous newspaper, it would be a "small revolution", reacted Nitzan Gonen, director of the Sex Determination Lab at Israeli Bar-Ilan University.
The quest to produce babies from parents of the same sex has been agitating the small world of biologists and geneticists for more than a decade.
The goal is not only to demonstrate the possibility for homosexual couples to have children without the intervention of an individual of the opposite sex, but also to open therapeutic doors for sterile people or for single-parent families, points out the Guardian.
But for now, Katsuhiko Hayashi's work remains confined to the animal kingdom.
He succeeded in reprogramming male mouse cells to lose their Y chromosome – a sex marker for men – and acquire a second X chromosome, which is only present in women.
"Some stem cells naturally lose their Y chromosome, while others, due to malformations or errors that scientists have sought to stimulate by adding a particular molecule, may acquire an X chromosome," Nitzan Gonen notes.
The work of Japanese scientists is therefore based on a subtle mixture of natural selection and human manipulation.
The new oocyte thus created – that is to say a female sex cell – was then fertilized by the researchers using mouse sperm.
The egg was then implanted into a female mouse to grow.
There is therefore still a "woman" who intervenes in the process, but "only because we have not yet developed an artificial uterus to ensure the proper development of the embryo in the laboratory", notes Robin Lovell- Badge, biologist and geneticist at the Crick Institute in London.
But this surrogate female does not transmit any genetic baggage to the future mouse who owes everything to his two dads.
An ineffective method
"This is scientifically very interesting and promising work, but we must also be aware of the current limits and the path still to be accomplished", warns Robin Lovell-Badge.
First, by Katsuhiko Hayashi's own admission, it's not yet a very effective method.
Out of 630 embryos implanted in surrogate females, only seven mice were born.
The good news is that these little ones have all grown well and become fertile, points out the magazine Nature.
"The production of gametes [male or female reproductive cells, Editor's note] is a very complex and long process. We do not know how to perfectly reproduce it in vitro", assures Nitzan Gonen.
In addition, "eggs produced in the laboratory and thanks to this method are of lower quality than those which are formed naturally", adds Robin Lovell-Badge.
Therefore, the number of viable embryos will be lower in this configuration.
“It will clearly be necessary to improve the effectiveness of this method before thinking of testing it on humans”, assures Nitzan Gonen.
And the path to a possible application of this discovery to humans is likely to be long and strewn with pitfalls.
First of a purely scientific order.
"We have not yet mastered the technology for humans that has been used here to transform a stem cell from a male mouse into an oocyte", underlines Robin Lovell-Badge.
The process would also take much longer.
“It would be a technical challenge of a whole new magnitude, because the integrity of the samples in the laboratory would have to be maintained over a much longer period, which multiplies the risk of accidents”, explains Robin Lovell-Badge.
Ethical Barriers
And that's without counting the ethical obstacles.
“It will be necessary to ensure that society is ready to accept the possibility that couples of men can have children,” said Nitzan Gonen.
“There will probably be a significant part of the population who will not object to this possibility, but another will oppose it for religious or other reasons. It will take time to think, upstream, of the arguments to justify this technology", notes Robin Lovell-Badge, who has already participated in national debates in the United Kingdom on the ethics of stem cell research.
Consideration should also be given to the place of women in this process.
The same questions that have agitated and continue to agitate in certain countries the debates on the role of surrogate mothers should come back to the table.
The technique used by Katsuhiko Hayashi also does not yet work for two mothers.
“While we roughly know how to create an oocyte from a male stem cell, no one has yet succeeded in making a sperm from a female stem cell,” explains Nitzan Gonen, whose laboratory works , among others, on this issue.
So many obstacles which, for her, mean that if this technology can one day be used for humans, it will probably not be "for ten or twenty years".
And it could then be used in much less controversial cases, such as to help couples with fertility problems.
"This technology could help people suffering from infertility, provided it is not a purely genetic problem," notes the biologist.
This method could thus represent a solution for people who have become sterile after cancer treatment.
"There are, for example, children who have overcome leukemia thanks to chemotherapy or radiotherapy. But these treatments can affect their fertility. This technique of creating oocytes from cells could help them", explains Robin Lovell -Badge.
Ditto for couples who decide to have children at a relatively advanced age "when the quality of the reproductive cells has deteriorated", adds Nitzan Gonen.
For the time being, therefore, it is a small step for the mice which, perhaps one day, will become a giant leap for humanity.
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