For the first time, US and Japanese scientists have genetically modified sperm, grown it in a laboratory dish and used it to produce a transgenic creature.
The technique could, in the long term, pay off in human fertility research and suggests new ways to overcome genetic disorders. So far, however, it only works for zebrafish.
Zebrafish have become a laboratory favourite because their embryos are transparent: geneticists can in effect see genes at work in the developing fish. Shawn Burgess of the US National Human Genome Research Institute, and colleagues at Fukui Prefectural University in Obama, Japan, report in the Proceedings of the National Academy of Sciences today they have developed techniques to make GM zebrafish using sperm cells grown entirely in laboratory conditions.
"To our knowledge, this is the first time that sperm cells have been cultured entirely in vitro and used to produce a transgenic animal," Dr Burgess said. Eric Green, the institute's scientific director, said: "This is an outstanding example of our efforts to build upon the foundation laid by the human genome project. Development of such novel technologies and methods will be essential for translating our rapidly growing knowledge of the genetic basis of disease into better diagnostic approaches and therapeutic options."
Most genetic engineering begins with the fertilised egg: the fusion of two inherited lines. But many inherited diseases are passed only through one parental line. Researchers have tried to genetically engineer sperm cells before allowing fertilisation to take place, but have been foiled because the altered sperm cells do not mature in laboratory conditions.
The US-Japanese team's landmark achievement was to genetically modify the sperm and then use it to successfully fertilise an egg. They found a way of enabling immature sperm cells from male zebrafish to survive long enough in laboratory culture to take aboard foreign genes, delivered by a retrovirus.
The sperm cells then develop into mature functional sperm which can be used for in vitro fertilisation - the standard IVF approach already used in human fertility treatment - to produce first transgenic embryos, and then ultimately fish. - (Guardian Service)