Abhinav Jain
12 October 2020
A recent article published in The New York Times described a set of rare individuals who are unable to identify funky odours, especially rotten fish which is widely circulated in social media. This describes the work of Gisladottir et al. on olfactory genes in the Icelandic population.
Olfactory senses are one of the oldest and most critical senses for the organism survival that helps in identifying food, potential mating partners, as well as dangers. Due to the variation in the number of olfactory receptors in the species, different species have different olfactory abilities[1]. These olfactory receptors (OR) are encoded by OR genes[2]. In humans out of 855 OR genes, only ~400 were functionally coded for ORs[3]. The genetic variation in the OR genes among individuals provides the personalized olfaction behaviour among individuals[3,4]. A number of association studies for odor perception with genetic OR loci are reported[5–7]. Also, a recent genome-wide association study was performed by Gisladottir et al. for odor perception on 9,122 Icelanders. They found three genetic variants i.e. p.Ser95Pro in TAAR5 gene (rs41286168), p.Lys233Asn in OR6C70 (rs60683621) and intergenic variant rs317787 associated with aversion to fish odor, increased intensity of licorice, and cinnamon odor respectively[8].
The availability of whole genome sequences as part of the IndiGen programme of over 1000 genomes of cosmopolitan Indians provides a unique opportunity to understand genetic epidemiology of functional variants in the population. Analysis of the IndiGen dataset revealed seven individuals were carrier for a rare variant rs41286168 with minor allele frequency (MAF) of 0.34% that is lower in comparison to the icelander population with MAF of 2.2%. While other two common variants rs60683621 and rs317787, spread all over India with MAF 19.14% and 54.88% respectively.
References
1. Sarafoleanu, C., Mella, C., Georgescu, M. & Perederco, C. The importance of the olfactory sense in the human behavior and evolution. J. Med. Life 2, 196–198 (2009).
2. Malnic, B., Godfrey, P. A. & Buck, L. B. The human olfactory receptor gene family. Proc. Natl. Acad. Sci. U. S. A. 101, 2584–2589 (2004).
3. Hasin-Brumshtein, Y., Lancet, D. & Olender, T. Human olfaction: from genomic variation to phenotypic diversity. Trends Genet. 25, 178–184 (2009).
4. Olender, T. et al. Personal receptor repertoires: olfaction as a model. BMC Genomics 13, 414 (2012).
5. Trimmer, C. et al. Genetic variation across the human olfactory receptor repertoire alters odor perception. Proc. Natl. Acad. Sci. U. S. A. 116, 9475–9480 (2019).
6. Mainland, J. D. et al. The missense of smell: functional variability in the human odorant receptor repertoire. Nat. Neurosci. 17, 114–120 (2014).
7. Jaeger, S. R. et al. A Mendelian trait for olfactory sensitivity affects odor experience and food selection. Curr. Biol. 23, 1601–1605 (2013).
8. Gisladottir, R. S. et al. Sequence Variants in TAAR5 and Other Loci Affect Human Odor Perception and Naming. Curr. Biol. (2020) doi:10.1016/j.cub.2020.09.012
About the Author
Abhinav Jain is a graduate student at the CSIR Institute of Genomics and Integrative Biology and his research is centered around the genomics and genetic epidemiology of Primary Immunodeficiency Disorders. He can be reached on twitter at @Abhinav_Jain_19.
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