Science: Biologists fail to repeat gene transfer by sperm


By DAVID DICKSON MOLECULAR biology has been thrown into the middle of its own ‘cold fusion’ affair by the failure of biologists in both the US and Europe to replicate a series of experiments which, it is being claimed, successfully demonstrateda revolutionary new method of insertingforeign genes into mice. Earlier this year, Marialuisa Livitrano and his colleagues in Rome announced that they had succeeded in ‘sticking’ small pieces of DNA on to the head of mice sperm. They subsequently used these sperm to fertilise mouse eggs, and reported that about 30 per cent of the offspring that resulted expressed the genetic information that had been transferred in this way (Cell, vol 57, p 717). If substantiated by others, the research would have widespread implications not only for creating transgenic mice, but for the whole field of genetic transplantation. At present, introducing new genetic material into mice embryos requires a relatively complex procedure of microinjection. The results reported by the Italian scientists promised a much simpler technique which, according to some estimates, wouldincrease the efficiency of producing transgenic mice by between two- and five-fold. As a result, the findings of Livitrano and his colleagues were welcomed with guarded enthusiasm when first announced. At the same time, however, a certain scepticism was expressed by some scientists in the field who had been trying unsuccessfully over many years to develop similar techniques, and who found it difficult to believe the sudden success reported by a relatively unknown research group. At the time, these scientists emphasised that no judgment could be passed until attempts had been made to replicate the experiments. This has now been done, and according to a scientific letter just published in the journal Cell by four leading researchers in the US, the results achieved so far by other laboratories who have repeated the Italian experiments are not optimistic (Cell, vol 59, p 239). Under the guidance of Ralph Brinster, Eric Sandgren and Richard Behringer of the University of Pennsylvania’s School of Laboratory Medicine, and Richard Palmiter of the Howard Hughes Medical Institute of the University of Washington, eight separate experiments were carried out using the techniques described by the Italian scientist. To ensure that the experimental conditions were as close as possible to those reported in the initial experiments, the American team was provided by the Italians with reagents and two samples of the DNA which had been used originally. Despite this, the American scientists report that ‘there was no indication that the foreign DNA was present in any of the fetuses or weanlings produced in these experiments’. Other laboratories are also drawing a blank, they say. ‘Despite a wide range of conditions and individual scientists involved, none of these laboratories have obtained transgenic mice by sperm-mediate transfer of foreign DNA.’ The Italian scientists have responded to these comments by suggesting that the inability of others to reproduce the original experiments ‘suggests the existence of a serious problem of which we were not aware’. In a response to the letter from Brinster and his colleagues, they say that they have started a new series of experiments to try to repeat the earlier work, and are also planning a series of experiments ‘in another laboratory in the near future’. At the same time, the Italians maintain confidence in their initial conclusions. Indeed,
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