Awkward Niff or so much fun?Studies show genetic variation in how fish odors are perceived

By claiming to be the largest genome-wide association study (GWAS) of olfactory genes, Icelandic researchers influence genetic variation in how people perceive fish odor intensity and discomfort. Has been identified. Many people find the smell of fish very unpleasant, but a new study and sniff test involving more than 9,000 people in Iceland showed that a mutation in a particular gene weakened the smell of fish. Researchers have also identified other genetic mutations that affect the ability to discriminate licorice and cinnamon odors.

“We have discovered sequence variants that influence how we recognize and explain the smell of fish, licorice, and cinnamon,” said deCODE Genetics and Dr. Rosa Gisladottir of the University of Iceland. Current biology. “Our sense of smell is so important to our perception of taste that these variants can affect whether we like foods that contain these smells.” Universities in Iceland and Sweden. Gisladottir and colleagues, who belong to, reported on their findings in a paper titled:Sequence variants of TAAR5 and other loci affect human odor perception and naming.. “

The human sense of smell is important for a variety of functions and provides us with a “rich understanding of our social and physical environment,” the author writes. Researchers already know that our ability to perceive odors is achieved by the olfactory receptors (OR), which are encoded by 855 olfactory receptor genes. However, about half of these human genes are thought to be deficient and are classified as pseudogenes, leaving a relatively small repertoire of about 400 active olfactory receptor genes.

The reason why so many of these olfactory genes in humans have been lost remains a mystery. “While the functional OR repertoire varies significantly between species, the inactivation of the OR gene is particularly large in primate strains for unknown reasons,” the team said. “The OR repertoire has more loss-of-function mutants of the OR gene than any other gene class, suggesting an unusually high sequence diversity of the intact OR gene compared to other protein-encoding genes. It has shrunk during human evolution. ”Also, it is not well understood how changes in the remaining active genes affect individual olfactory differences. “How is the genetic sequence diversity of this unusual class of genes transformed into perception and behavior?” Asked the investigator.

To explore this further, Gisladottir, along with the corresponding deCODE author Kari Stefansson and his team, enlisted 9,122 Icelanders in GWAS in search of OR gene variants that affect odor perception. It was. They asked study participants to smell the scent presented to them with a pen-like device that gave off a specific scent when uncapped. After the participants sniffed each scent pen, the researchers asked them to name the scent. Participants also evaluated the strength and comfort of each scent. The odors tested contained the major ingredients found in licorice, cinnamon, fish, lemon, peppermint and bananas.

Through analysis of the loci of interest, the team identified mutations associated with odor perception and naming differences. We then confirmed the findings in another cohort of 2,204 Icelanders. One of the variants involved in odor perception was identified by a non-standard olfactory receptor gene called the trace amine-related receptor 5 (TAAR5). TAAR5 variants have been found to affect the perception of rotten and fermented fish, other animal odors, and the odor of fish containing trimethylamine, a bacterial metabolite found in various body fluids.

In odor tests, people with certain variants of the TAAR5 gene are more likely to smell nothing when presented with a fish odor, or to use descriptors of neutral or positive, non-seafood-related odors. became. “Potato,” “caramel,” and “rose” researchers said the finding was the first to show the important role of this gene in humans. “TAAR5 encodes a member of the TAAR family of trace amine-related receptors, which function as chemosensory receptors in the olfactory epithelium of vertebrates and are G protein-coupled to detect volatile and often aversive amines. It is a type receptor (GPCR). There are no previous reports of TAAR5 sequence variants that affect the human sense of smell. “

Gisladottir commented: “Variant carriers have a weaker fish odor, less discomfort, and are less likely to be named correctly. There are many animal studies on TAAR5 related to their role in hard-wired aversion to trimethylamine. Our findings extend the meaning of this study to human odor perception and behavior. “

The other two findings are associated with more typical and common olfactory gene mutations. These varieties affected an individual’s ability to name the scent of licorice and cinnamon. They also affected the strength and comfort associated with their odor. “We found a common variant of the olfactory receptor cluster associated with increased susceptibility to transanethole, found not only in black licorice products, but also in spices and plants such as anise seeds, star anise, and fennel. “I did,” continued Gisladottir.

“Variant carriers can be named with a stronger licorice odor, more pleasing and more accurate. Interestingly, this variant is much more common in East Asia than in Europe.” Cinnamon variant. Affects the perception of transcinnamaldehyde, the main component of both Chinese cinnamon and Ceylon cinnamon. The team reported that the carrier of this variant was able to name the cinnamon odor more accurately. Carriers have also found that the odor is stronger.

Combined findings indicate that changes in olfactory genes affect human odor perception. “Overall, our results provide a unique window to the effects of sequence diversity on the human sense of smell,” the team concluded. “A personalized OR repertoire makes a myriad of differences in perception and behavior, including the olfactory language we are just beginning to understand.”

Newly reported results also show that humans have fewer olfactory genes than other species, but some of the genetic variations that people have are more sensitive to specific odors such as licorice and cinnamon. Indicates that “Coupled with evidence of geographical differences in allele frequencies, this may indicate that the widespread sequence diversity found in human olfactory receptor genes that affect our olfaction is still being sharpened by natural selection. It enhances sex, “the researchers suggested. They aim to continue collecting data on people’s perception of odors and also plan to use the same olfactory task to investigate odor deficiencies in the context of COVID-19.