By
The Associated Press
Scientists have identified the first human gene that may be linked to pheromones, odorless molecules that in other animals trigger primal urges including sex, defense and kinship.
Experts describe the discovery as possibly opening a new door into the role of pheromones in human development.
In animals, researchers have documented how pheromones trace complex neurological paths 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 they had been unable to find any of the equipment needed to detect these potent molecules.
Now, in experiments at Rockefeller University and Yale, neurogeneticists have isolated a human gene, labeled 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 that accepts only a specific key.
''This is the first convincing identification of a human pheromone receptor,'' said University of Colorado biochemist Joseph Falke.
Humans share the V1RL1 gene with rodents and other mammals that rely heavily on pheromone cues to survive.
However, it has not been determined whether the gene is active in humans or which pheromone-induced 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,'' 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, called V1RL1, subsequently was found in 11 out of 11 randomly chosen people from varying ethnic backgrounds, researchers said.
While rodents and other creatures essentially are reactive animals that depend heavily on pheromones for behavioral cues, humans use their larger brains to rely more on judgment and complex sensory cues, such as vision.
''In mice, we think there are more than 100 functioning genes in the V1r family,'' said Ivan Rodriguez of Rockefeller University, lead author of the study. ''But in humans, V1RL1 may very well be the sole functioning gene in the family.''
''Why has it hung around all this time?'' said Charles Wysocki of the Monell Chemical Senses Center in Philadelphia. ''It must be very important if it has outlived all of its predecessors.''
Scientists aren't sure what happened to the other 99 genes.
''It's unheard of that a family of 100 genes in mice is reduced to a single gene in humans,'' said the study's senior author, Peter Mombaerts.
In most mammals, pheromones usually are 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. However, the VNO in humans shrinks and stops working before birth.
Researchers have long suspected that humans communicate with pheromones. But how pheromones are produced and how they are detected across a room, or even greater distances, is poorly understood.
One 1998 study at the University of Chicago demonstrated that pheromones in underarm sweat prompt women living in close quarters to synchronize their menstrual cycles.
Some companies put pheromones in perfumes. Chemical makers bait insect traps with pheromones.
Mombaerts said it is too early to tell whether the gene discovery might lead to pheromone-based medicines.
However, the potential for pheromone misuse worries some researchers and bioethicists.
''Safeguards will be needed to prevent the manipulation of human behavior,'' Falke said. ''We won't want pheromones showing up in magazine ads, or pumped through ventilation systems at the mall.''
