Scientists Create Mice With Two Fathers After Making Eggs From Male Cells

Scientists have created mice with two biological fathers by generating eggs from male cells, a development that opens up radical new possibilities for reproduction. The Guardian reports: The advance could ultimately pave the way for treatments for severe forms of infertility, as well as raising the tantalizing prospect of same-sex couples being able to have a biological child together in the future. "This is the first case of making robust mammal oocytes from male cells," said Katsuhiko Hayashi, who led the work at Kyushu University in Japan and is internationally renowned as a pioneer in the field of lab-grown eggs and sperm. Hayashi, who presented the development at the Third International Summit on Human Genome Editing at the Francis Crick Institute in London on Wednesday, predicts that it will be technically possible to create a viable human egg from a male skin cell within a decade. Others suggested this timeline was optimistic given that scientists are yet to create viable lab-grown human eggs from female cells. The study, which has been submitted for publication in a leading journal, relied on a sequence of intricate steps to transform a skin cell, carrying the male XY chromosome combination, into an egg, with the female XX version. Male skin cells were reprogrammed into a stem cell-like state to create so-called induced pluripotent stem (iPS) cells. The Y-chromosome of these cells was then deleted and replaced by an X chromosome "borrowed" from another cell to produce iPS cells with two identical X chromosomes. "The trick of this, the biggest trick, is the duplication of the X chromosome," said Hayashi. "We really tried to establish a system to duplicate the X chromosome." Finally, the cells were cultivated in an ovary organoid, a culture system designed to replicate the conditions inside a mouse ovary. When the eggs were fertilized with normal sperm, the scientists obtained about 600 embryos, which were implanted into surrogate mice, resulting in the birth of seven mouse pups. The efficiency of about 1% was lower than the efficiency achieved with normal female-derived eggs, where about 5% of embryos went on to produce a live birth. The baby mice appeared healthy, had a normal lifespan, and went on to have offspring as adults. "They look OK, they look to be growing normally, they become fathers," said Hayashi. He and colleagues are now attempting to replicate the creation of lab-grown eggs using human cells.

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