Scientists Break Barriers, Deliver Mouse Offspring with Two Fathers in Revolutionary Study ,A new breakthrough in egg creation has allowed a female mouse to give birth to babies carrying only the genes of two fathers.
The scientists did this through genetic engineering, turning male XY chromosomes into female XX chromosomes and creating eggs from purely male skin cells.
“The mice look good—they’re grown adults, and adult mice are also fertile,” says Katsuhiko Hayashi, a genomic biologist at Osaka University in Japan.
The achievement has enormous implications for same-sex parenting and for treating or preventing sex chromosomal disorders such as infertility and Down syndrome.
“It was surprising – I’m happy to get these results,” says Hayashi.
Genetically modified mice
Hayashi and his colleagues have been working on this technique for 12 years. This basically involves creating a stem cell from a somatic cell.
In multicellular organisms, somatic cells are any type other than reproductive cells. Using a technique developed by Nobel laureate Shinya Yamanaka, Hayashi’s team introduced genes into somatic cells to turn them into pluripotent stem cells, a type of cell that can replace an embryonic cell.
In March study published in Naturethe team describes how they used this technique to convert an XY male chromosome into an XX female chromosome in mice.
Changing the chromosomes of mice
Basically, they took the chromosomes from the tip of the tail of a male mouse, changed them to a female chromosome, then added them to the chromosomes of another male.
They still needed a female mouse to carry the eggs they created and give birth, but the essential chromosomes did not come from the surrogate female.
Using this technique, the team implanted embryos into surrogate women, who then gave birth to seven healthy babies—six males and one female. However, the success rate was generally low.
Only 1.1% of the 630 mice implanted with embryos survived.
But those seven survivors also became fertile — both male and female offspring had babies of their own, Hayashi says.
Read more: How stress, climate and trauma can cause sexual changes in nature
Implications for Down syndrome
Because the technique can alter chromosomes, it can also fix potential problems.
One condition that may be affected is Down syndrome or trisomy 21, which occurs when a person carries an extra copy (partial or complete) of chromosome 21. (Most people carry exactly two copies of the 23 chromosomes that make up their genome).
Mice’s chromosomes are not exactly the same, but some mice, like humans, carry a disorder called trisomy 16, which can lead to the death of the affected fetus or developmental problems after birth.
Hayashi’s technique also eradicated the trisomy 16 problem in mice.
Since trisomy 16 has been used as a model of Down syndrome in humans, it is possible that this technique could be further developed to help prevent this condition.
Coping with infertility
It can also help reverse infertility in cases where the problem involves too many Y chromosomes or the loss of an X chromosome.
If developed further, same-sex couples could have babies that carry both of their genes. “[This study] opens up the possibility of bipaternal reproduction,” the authors say in the study.
Read more: My long and arduous journey through the frontiers of fertility technology
Conservation Aid
The breach also has implications for the conservation of endangered species.
In the future, this technique could be extended to help in cases where few individuals of a species remain.
For example, there are only two northern white rhinos left in the world, and both are female. Wildlife explorer Thomas Hildebrand told CNN that this technique can help the breeding program of these specific animals.
The risks of genetic engineering
Of course, this experiment was only conducted on mice, and a lot of work will be needed before someone uses a similar technique on humans.
“We are at least certain that this is possible using experimental animals,” says Hayashi.
Like development of human cloningthere are also some ethical issues to consider.
Hayashi says societies will need to have conversations about the ethics of making changes to these basic building blocks of biology before something like this is done on humans.