A mouse has been created in the laboratory by a technique that does away with the need for males in reproduction, a breakthrough that raises the prospect of fatherless babies.
A mouse has been created in the laboratory by a technique that does away with the need for males in reproduction, a breakthrough that raises the prospect of fatherless babies.
The mouse was generated from two unfertilised eggs and its birth has demonstrated for the first time that it is possible for mammals to be born by the "virgin birth" phenomenon of parthenogenesis.
Scientists said the mouse developed normally to adulthood and had offspring of its own by normal sexual reproduction, showing parthenogenesis could work on warm-blooded mammals, including humans.
Experts said the technique was far too complicated and risky to use on humans. But if the problems can be overcome and if experiments on other mammals can demonstrate the process can be made safe, there will undoubtedly be pressure from some quarters to apply parthenogenesis to treat human infertility. If so, it begs the question about the need to have men involved in reproduction.
Tomohiro Kono, the scientist at Tokyo University who led the research, dismissed the possibility of using parthenogenesis on humans as a "senseless question".
Asked by The Independent whether it would be possible in theory to produce a human baby by the same technique, Dr Kono replied: "No answer for empty question. Very sorry."
The British team who created Dolly the cloned sheep was given a licence last year by the Human Fertilisation and Embryology Authority (HFEA) to activate human eggs using parthenogenesis to generate embryonic stem cells, but not to produce embryos for implanting into a woman's womb.
The HFEA said its decision was partly justified because human eggs activated during parthenogenesis did not have the potential to develop into a child, a statement now undermined by the Japanese research in the journal Nature.
Parthenogenesis differs from the cloning technique used to create Dolly because it results in embryos developing entirely from unfertilised eggs rather than embryos resulting from eggs combined with the ordinary cells of the body. Dr Kono's team used 598 mouse eggs to generate enough viable embryos by parthenogenesis to impregnate 26 females, resulting in 24 pregnancies.
Of the 10 live and 18 dead foetuses, two survived birth and just one lived long enough to develop into an apparently normal adult female, which the researchers have named Kaguya. In effect, Kaguya has two genetic mothers. She was created by merging the chromosomes of a genetically altered mouse with an egg from another mouse.
Until this study, it was thought to be impossible for mammals to reproduce by parthenogenesis, a method of reproduction common in reptiles and insects where identical female offspring can be quickly produced when resources are limited. Dr Kono said his study had shown that the crucial barrier to parthenogenesis in mice and other mammals appeared to be a process of genetic "imprinting" when paternal and maternal genes were selectively turned off and on.
Professor Alison Murdoch, chair of the British Fertility Society, said imprinting was thought crucial in several stages in the development of the human embryo. Understanding it better would elucidate disorders, she said. "This is an important scientific development that will help us understand genetic imprinting and why babies are born with abnormalities."
Dr Kono's team admitted many of the embryos and foetuses in the parthenogenesis experiment were abnormal. Leading scientists said this showed it was far too dangerous to use the technique for human reproduction.
Martin Bobrow, professor of medical genetics at Cambridge University, said: "Ethically, the arguments for and against applying this to human beings would be much the same as for other cloning techniques. Whether it is more or less safe remains to be seen."
Simon Best, chairman of the Biotechnology Industry Association in Scotland, said the inefficiency and abnormalities of parthenogenesis made it even more unacceptable than cloning. "The [study] shows that, like cloning, another asexual form of reproduction is possible in mice and may be possible in some other mammals," he said. "But this was achieved with even lower efficiency than the cloning process used to make Dolly, so it is even more unacceptable and unsafe to consider using this for humans."
Professor Azim Surani, professor of physiology and reproduction at Cambridge University, said: "This is an incredible achievement. The process of creating these mice required perseverance and patience. But from 600 eggs only two mice were created. This technique is far too complicated to be used in humans."
Anne Ferguson-Smith, clinical director of Centres for Assisted Reproduction, said the study showed parthenogenesis work-ed on only a tiny proportion of mouse embryos. "This does not mean that males are obsolete," she said. "The requirement for paternal chromosomes for normal development is still with us."
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