Germline gene therapy advance

Canadian scientists have produced mice with an artificial chromosome that was successfully passed on to their offspring. Reporting in London last week at a conference on biotechnology, the Canadian company responsible, emphasised that they have no intention of repeating the experiment in humans and plans instead to use the technology to produce herds of genetically modifiedanimals whose milk will contain pharmaceuticals.

Researchers at Chromos Molecular Systems, based in British Columbia, inserted an artificial chromosome into the cells of mice embryos. That chromosome was subsequently taken up by every cell in the mice's bodies - including the sperm and egg cells. When the transgenic mice mated with normal mice, the artificial gene was inherited safely without interfering with the rest of the genome. 'Because the artificial chromosome is separate, it doesn't interfere with the cell's own genetic machinery,' said Eileen Utterson, vice-president of corporate development.

Cromos is also working on human artificial chromosomes for use in conventional, non-germline genetic therapy. Artificial chromosomes have the advantage of being able to carry much more DNA than is possible with current methods which use viruses or plasmids. But the company stressed that it won't allow the technology to be used for human germline engineering.