Mouse pups with same-sex parents created by Chinese scientists
Using advanced new gene-editing techniques, scientists from the Chinese Academy of Sciences have produced healthy, viable mouse babies using DNA taken from two mothers — without a father in sight.
According to a paper published in the journal Cell Stem Cell, the team also created mice with two dads, but these offspring only survived for a couple of days. The idea behind the research was to investigate why it’s so challenging for mammals of the same sex to produce offspring and how these barriers can be overcome.
“Although animals have three different reproduction modes, known as asexual reproduction, unisexual reproduction and sexual reproduction, mammals can only undergo sexual reproduction,” Qi Zhou, a senior author of the study, told Newsweek. “How does this happen? We got interested in this question.”
While some reptiles, amphibians, fish and other animals can reproduce with one parent of the same sex, mammals do not have this capability. Even with lab fertilization technologies, it is very difficult to achieve.
The reproduction in mammals
“It had been thought that reproduction in mammals was predicated on receiving DNA from both maternal and paternal origin as eggs and sperm have a different yet complementary pattern of coding,” Megan Munsie, Deputy Director of the Centre for Stem Cell Systems at the University of Melbourne, who was not involved in the study, said in a statement. “This patterning is referred to as imprinting and is imposed during sperm and egg development in mammals.”
As a result, mammal offspring that don’t receive genetic material from both a mother and a father could experience developmental abnormalities or may not be viable.
However, the Chinese researchers were able to create pups solely from female genetic material using embryonic stem cells—which are capable of turning into any other cell—that contained only a single set of chromosomes rather than the pairs that are usually present in mouse cells.
The researchers deleted several regions of the genome in the haploid stem cells to remove the imprinting genes. These modified stem cells were then injected into normal eggs (from another mouse) to create embryos that were transplanted into a surrogate mouse.
This resulted in the birth of 29 healthy pups, which lived to adulthood and were even able to have offspring of their own. The process was inefficient, however, with only a small proportion of the 210 embryos used developing into a pup.
Previously, researchers have produced bimaternal mice—mice with two mothers— however, the technique used in this case was not as practical as the latest method and the offspring displayed several abnormalities.
To create the pups from only male genetic material, the team used a similar process to how they created the bimaternal pups, albeit slightly more complicated.
“Again, they injected the nucleus from genetically modified male haploid stem cells, alongside sperm from another mouse, into eggs where the female chromosomes were removed,” Munsie said. The “resulting embryos were then allowed to develop in the lab for several days.”