Gene transfer puts good fats in mammals.

Aiming ultimately to make healthier beef, eggs, and other farm products, scientists have used a worm gene to genetically engineer mice whose tissues are unusually rich in the heart-healthy fats found mainly in fish.

Compared with red meat and poultry, fish such as trout and salmon contain large quantifies of omega-3 fatty acids. These are more healthful fats than the omega-6 group, which tends to dominate Western food choices.

With an eye toward shifting that balance, the scientists inserted into mice a gene called fat-1, which in nematode worms produces an enzyme that converts omega-6 fats into omega-3 fats.

To see whether the transplanted gene had any effect, the researchers, led by Jing X. Kang of Massachusetts General Hospital in Boston, "raised the genetically engineered mice and unmodified mice on the same diet. After 8 weeks, muscle from the normal mice contained nearly 50 times as much of the omega-6 fats as omega-3 fats, but the engineered animals' muscles contained less omega-6 fats than omega-3 fats, the scientists report in the Feb. 5 Nature. It's not yet clear whether the gene would have a similar effect on cows and chickens.--B.H.