Scientists have created baby mice with two fathers for the first time.
They turned male mouse stem cells into female cells in a lab.
The work was described in a study published Wednesday in the journal Nature.
The researchers took skin cells from the tails of male mice and converted them into "induced pluripotent stem cells," which have the ability to develop into many different types of cells or tissues.
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Next, by growing and treating the male stem cells with a drug, they were turned into female cells and produced functional egg cells.
Those eggs were fertilized, and the scientists implanted the embryos into female mice.
About 1% of the embryos grew into live mouse pups that appeared to grow normally and became parents themselves, research leader Katsuhiko Hayashi of Kyushu University and Osaka University in Japan told fellow scientists at the Third International Summit on Human Genome Editing last week.
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In commentary published alongside the study, Diana Laird, a stem cell and reproductive expert at the University of California, San Francisco, who was not involved in the research, said the work "opens up new avenues in reproductive biology and fertility research" for animals and people.
"And it might even provide a template for enabling more people," such as male same-sex couples, "to have biological children, while circumventing the ethical and legal issues of donor eggs," she and colleague Jonathan Bayerl said.
They also raised several cautions, including that the technique is extremely inefficient. They also stressed that it’s still too early to know if the protocol would work in human stem cells at all. And Laird highlighted that scientists need to be mindful of the mutations and errors that may be introduced in a culture dish before using stem cells to make eggs.
The Associated Press contributed to this report.
