Tuesday, August 24, 2021

Amoore' Anosmias Get a Tune-Up

Back in the 1960's, a scientist named John Amoore tried to get a number on how much our sense of smell varies from person to person. In his study (limited mostly to Europeans), he found that half are anosmic to something. That was long before we sequenced the human genome. This study goes a bit further:

There's a gene for detecting that fishy smell, olfactory GWAS shows
Oct 2020, phys.org
9,000 people in Iceland showed that not only do they smell licorice and cinnamon differently, but there's a mutation that makes rotten fish smell a little less fishy. (The odors they used weren't limited to these three, there were also lemon, peppermint, and banana.)

One of the genes is called a "non-canonical olfactory receptor gene" or a trace amine receptor, TAAR 5 in this case. People with a particular variant of this gene were more likely to not smell anything when presented with the fish odor or to use descriptors for it that were neutral or positive and not seafood related, such as "potatoes," "caramel," and "rose."

"Carriers of the variant find the fish odor less intense, less unpleasant, and are less likely to name it accurately," Gisladottir said. 

"We discovered a common variant in a cluster of olfactory receptors which is associated with increased sensitivity to trans-anethole, found in black licorice products but also in spices and plants such as anise seed, star anise, and fennel," Gisladottir said. "Carriers of the variant find the licorice odor more intense, more pleasant, and can name it more accurately. Interestingly, the variant is much more common in East Asia than in Europe."

The cinnamon variant influenced the perception of trans-cinnamaldehyde, the major ingredient in both Chinese and Ceylon cinnamon. Carriers of the variant can name the cinnamon odor more accurately, they report. They also find it more intense.

via deCODE Genetics in Reykjavik, Iceland: Current Biology, Gisladottir et al.: "Sequence variants in TAAR5 and other loci affect human odor perception and naming. DOI: 10.1016/j.cub.2020.09.012

Post Script:
Here's another way to measure the difference in how we smell things -- we have a 30% variation from person to person:
378-dimensional individual olfactory receptor subtype genome:
Individual olfactory perception reveals meaningful nonolfactory genetic information.
Secundo L, Snitz K, Weissler K, Pinchover L, Shoenfeld Y, Loewenthal R, Agmon-Levin N, Frumin I, Bar-Zvi D, Shushan S, Sobel N. Proc Natl Acad Sci U S A. 2015 Jul 14; 112(28):8750-5.

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