52: Mice Breed Without Fathers

By Helen PearsonJan 3, 2005 6:00 AM


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The rules of reproduction were rewritten this year when Japanese and Korean biologists bred mice without fathers. The feat was long considered impossible in mammals because embryos were thought to need the different sets of genes that are switched on in sperm and eggs. By contrast, fish, frogs, and insects regularly manage it through a process known as parthenogenesis. Scientists had tried previously to prod mouse eggs into parthenogenesis, but the embryos died after a few days.

The team, led by Tomohiro Kono of Tokyo University of Agriculture, began by taking an immature female egg from a genetically engineered mouse. Two of the mouse’s genes had been altered so that the egg had a pattern of gene activity similar to that of a sperm. The team then fused the nucleus of this pseudosperm with that of a normal, mature egg from another female. After 457 attempts, the team produced 10 live pups. One survived to adulthood. The mouse was called Kaguya, after the Japanese tale of a girl miraculously discovered in a bamboo stump. “It was a fantastic surprise,” Kono says. “I couldn’t believe my eyes.”

The results, striking as they were, hardly suggest that males are obsolescent, as some observers fretted. Creating a fatherless human would be risky as well as ethically objectionable: No one knows if the offspring would be healthy. Still, Kono is already attempting to conjure fatherless offspring from other species, including pigs.

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