By THE ASSOCIATED PRESS

Scientists have identified the first human gene that may be linked to pheromones, the odorless molecules that in other animals trigger primal urges including sex, defense and kinship.

Experts described the discovery as possibly opening a new door into the role of pheromones in human development. In animals, researchers have documented the complex neurological paths pheromones trace to stimulate parts of the brain that are deeply rooted in instinct. Researchers have long believed that humans also communicate through pheromones, but until now had been unable to identify any of the biological equipment needed to detect these potent molecules.

Now, in experiments at Rockefeller and Yale Universities, neurogeneticists have isolated a human gene, called V1RL1, that they believe encodes for a pheromone receptor in the mucous lining of the nose. A receptor is a patch on the surface of a cell that binds with specific molecules, like a lock accepting a key. "This is the first convincing identification of a human pheromone receptor," Joseph Falke, a biochemist at the University of Colorado, said.

Humans share the V1RL1 gene with rodents and other mammals that rely heavily on pheromone cues to survive. But it has not been determined whether the gene is active in humans or which behavior the gene might induce. "The ultimate test will be to find a pheromone that binds to the receptor and triggers a measurable physiological response," Dr. Falke said. The research was published in the September issue of the journal Nature Genetics. Researchers took samples from a gene bank and scanned them for matches to the rodent genes from the V1r family. They found eight matches in human genetic material. Further testing showed that seven of the eight human V1r genes are inoperative. The potentially functional gene, V1RL1, was subsequently found in each of 11 randomly chosen people from varying ethnic backgrounds, researchers said.

Rodents and other creatures essentially are reactive animals that depend on pheromones for behavioral cues. Humans use their larger brains to rely more on judgment and complex sensory cues, like vision. "In mice, we think there are more than 100 functioning genes in the V1r family," said Ivan Rodriguez of Rockefeller University, the main author of the study. "But in humans, V1RL1 may very well be the sole functioning gene in the family." Scientists are not sure what happened to the other 99 genes in the family. "It's unheard of that a family of 100 genes in mice is reduced to a single gene in humans," said the senior author of the study, Peter Mombaerts.

But Charles Wysocki of the Monell Chemical Senses Center in Philadelphia looked at it in a different light, saying: "Why has it hung around all this time? It must be very important if it has outlived all of its predecessors." In most mammals, pheromones are usually detected by a specialized organ inside the nose or mouth called the vomeronasal organ, or VNO. Nerves connect it to parts of the brain involved in reactions rather than cognition. In humans, the organ appears in embryos with its nerve cells extending into the developing brain. For several weeks, it serves as a pathway for hormones vital to sexual development and maturity. But the VNO in humans shrinks and stops working before birth.  

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