Blocked gene gives mice super smell.

Time to hide the cheese. Researchers have created a mutant mouse strain whose sense of smell is much sharper and more sensitive than that of typical mice. Oddly enough, they did so by inactivating a gene in the rodents, not by adding one.

The knocked-out gene encodes a protein called Kv1.3, which normally assembles into some of the membrane channels that control the flow of potassium ions in and out of cells and thereby regulate how readily nerve cells respond to stimuli.

Because the protein is found in cells of the olfactory bulb of mice, Debra A. Fadool of Florida State University in Tallahassee and her colleagues suspected that deactivating the gene might create rodents with a poor sense of smell. In the Feb. 5 Neuron, the researchers report the opposite result: Mice lacking Kv1.3 have a sense of smell 1,000 to 10,000 times as sensitive as that of typical mice and are better at discriminating closely related odors. The researchers speculate that variations in the corresponding human gene may account for differences in people's sense of smell.

Further study of the mutant mice revealed that the animals had smaller-than-average glomeruli, the odor-detecting units of the nose, but the rodents had many more of them than usual. The researchers haven't documented other profound physical or behavioral abnormalities in the rodents lacking the Kv1.3 gene.--J.T.