Abstract
The molecular mechanism of olfactory cognition is very complicated. Olfactory cognition is initiated by olfactory receptor proteins (odorant receptors), which are activated by olfactory stimuli (ligands). Olfactory receptors are the initial player in the signal transduction cascade producing a nerve impulse, which is transmitted to the brain. The sensitivity to a particular ligand depends on the expression level of multiple proteins involved in the process of olfactory cognition: olfactory receptor proteins, proteins that participate in signal transduction cascade, etc. The expression level of each gene is controlled by its regulatory regions, and especially, by the promoter [a region of DNA about 100–1000 base pairs long located upstream of the transcription start site (TSS)]. We analyzed single nucleotide polymorphisms using human whole-genome data from the 1000 Genomes Project and revealed an extremely high level of single nucleotide polymorphisms in promoter regions of olfactory receptor genes and HLA genes. We hypothesized that the high level of polymorphisms in olfactory receptor promoters was responsible for the diversity in regulatory mechanisms controlling the expression levels of olfactory receptor proteins. Such diversity of regulatory mechanisms may cause the great variability of olfactory cognition of numerous environmental olfactory stimuli perceived by human beings (air pollutants, human body odors, odors in culinary etc.). In turn, this variability may provide a wide range of emotional and behavioral reactions related to the vast variety of olfactory stimuli.
Highlights
Human olfactory perception varies enormously among individuals
At least one single nucleotide polymorphism (SNP) was found in the upstream regions of 81.5% of transcripts
FINAL CONCLUSIONS The majority of investigations of olfactory receptor (OR) genes demonstrate that genetic variability in coding regions of OR genes may be associated with differences in olfactory cognition and odor perception, confirming the idea of functional importance of coding SNPs
Summary
Human olfactory perception varies enormously among individuals. People vary both in their general olfactory acuity and in perceiving specific odors. According to a study of 391 adult subjects in New York, general olfactory acuity correlated with age, gender, race, smoking habits, and body type. Factors found to influence olfactory perception included race, age, and gender. Over 100 instances in which the intensity or pleasantness perception of an odor varied significantly among demographic groups were described (Keller et al, 2012)
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