Scientists create mice from two males in major breakthrough

It's pretty well known that usually two sexes have to be involved for reproduction, but a team of scientists in Japan might have just blown that assumption out of the water.

Led by Katsuhiko Hayashi, a professor of genome biology at Osaka University in Japan, the team have been able to create mice with parents who are both biologically male.

It marks a huge milestone in the topic of reproductive biology, and comes about after years of intricate and exhaustive lab work.

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The researchers began with some skin cells taken from the tails of two adult male mice, which had been grown in a lab. Like in male humans, these cells have one X and one Y chromosome.

The team then turned the cells into induced pluripotent stem cells (iPSCs) - a cell which scientists have previously reprogrammed into an embryonic state. When these iPSCs were cultured, a few spontaneously lost the Y chromosome, generating 'XO' cells.

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Looking at the cultured XO cells, the team found that some developed two X chromosomes as a result of cell division errors. As a result, they were chromosomally female, despite originating from male cells.

Prof. Hayashi, Osaka University

The team converted the XX cells into those which precursor eggs and sperm, and programmed them with the signals to turn them into egg cells. Then, once they were fertilized with sperm and implanted into a mouse uterus, some brand new baby mouse pups were born.

Hayashi noted that only seven out of 630 implanted mouse embryos resulted in living offspring, but the success rate wasn't down to the sex chromosome conversion. Instead, he explained it was simply because cells cultured in a lab are typically inferior to those in a living animal.

Though the research is only in its early stages, it holds promise for the question of whether same-sex couples could one day create children with both parents' genes.

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Speaking to CNN, the professor explained: “It (will be) difficult to produce babies from male-male (human) couples because of both technical and ethical reasons. But it is theoretically possible to produce babies from male-male couples, as shown in this study.”

However, Hayashi noted that it is more challenging to make sperm from female cells because they don't contain any of the essential Y chromosome.

Mike McGrew, Personal Chair of Avian Reproductive Technologies at The Roslin Institute at the University of Edinburgh, also noted that the technique could be promising when it comes to helping to save endangered species.

McGrew said that it's currently unknown whether the same spontaneous loss of a Y chromosome and the duplication of the X chromosome would occur in other mammal species, but he described the results as a 'very exciting finding for species conservation'.