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Genetic Variant Linked to Odor Perception

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Duke Health News 919-660-1306

DURHAM, N.C. -- Why the same sweaty man smells pleasant to
one person and repellant to another comes down to the smeller's
genes.

Duke University Medical Center researchers demonstrated that
genetic variants of odor receptors within the nose determine
how a particular odor is perceived. The researchers, led by
Duke's Hiroaki Matsunami, Ph.D., assistant professor of
molecular genetics and microbiology, published the results of
their experiments early online Sept. 16 in the journal
Nature.

The researchers focused on two chemicals – androstenone and
androstadienone – that are created naturally by the body during
the breakdown of the male sex hormone testosterone and are
excreted in sweat and urine.

"We found that genetic variations of a specific odor
receptor determine, to a significant degree, why the same
chemicals smell pleasant or unpleasant to different people,"
Matsunami said. "These results demonstrate the first link
between the functioning of a human odor receptor gene and how
that odor is perceived."

Humans have about 400 odor receptors within the nose that
detect various odors or chemicals. Smells typically bind to
their corresponding receptors, and the information is then
relayed to the brain for processing.

The researchers wanted to uncover the reasons why people
react differently when they smell these two sex steroid-derived
chemicals. Hanyi Zhuang, a student in the Matsunami laboraroty,
tested all the known smell receptors in the laboratory and
found one that reacted strongly with the two chemicals.

In conjunction with their collaborators at Rockefeller
University, the researchers asked 391 volunteers to inhale the
two chemicals and describe what they smelled. The results
ranged from no smell at all, to descriptions such as "vanilla
and sweet" and "sickening and urine." DNA extracted from blood
samples from each volunteer were sent to Matsunami's
laboratory.

"After performing genetic analysis on each of the samples
and correlating the results with the smell descriptions, we
were able to link specific genetic variants with specific
perceptions," Matsunami said. "While many theories of the
different perceptions of smell focus on culture, experience or
memory, our results show that an important portion of this
variability is due to an individual's genes."

Matsunami added that these results will likely add to the
debate over the existence of pheromones in humans. Pheromones
are chemical signals between animals that express alarm, mating
and navigation cues. In other species, they've been found to
trigger behavioral changes in the smeller.

"The sex-steroid odors that we tested in humans act as
pheromones in pigs, and there has been debate whether these
same chemicals act similarly in humans," Matsunami said. "There
is evidence that smelling these odors can affect the mood and
physiological state of both men and women."

Matsunami and his colleagues plan further studies to
understand how smelling these chemicals might affect human
social and sexual behavior.

He added that there are likely other receptors and receptor
variants that may also play roles in how these two chemicals
are perceived. Since it is known that there are about 400
specific smell receptors and humans can detect more than 10,000
different odors, it follows that different combinations of
receptor genes and variants must be involved in perceiving each
odor, he said.

Other members of the team were Qiuyi Chi from Duke and
Andreas Keller and Leslie Vosshall of Rockefeller. The research
was supported by the National Institutes of Health.

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