A transcriptomic atlas of mammalian olfactory mucosae reveals an evolutionary influence on food odor detection in humans

Abstract

The mammalian olfactory system displays species-specific adaptations to different ecological niches. To investigate the evolutionary dynamics of olfactory sensory neuron (OSN) subtypes across mammalian evolution, we applied RNA sequencing of whole olfactory mucosa samples from mouse, rat, dog, marmoset, macaque, and human. We find that OSN subtypes, representative of all known mouse chemosensory receptor gene families, are present in all analyzed species. Further, we show that OSN subtypes expressing canonical olfactory receptors are distributed across a large dynamic range and that homologous subtypes can be either highly abundant across all species or species/order specific. Highly abundant mouse and human OSN subtypes detect odorants with similar sensory profiles and sense ecologically relevant odorants, such as mouse semiochemicals or human key food odorants. Together, our results allow for a better understanding of the evolution of mammalian olfaction in mammals and provide insights into the possible functions of highly abundant OSN subtypes.

Non-neuronal expression of SARS-CoV-2 entry genes in the olfactory system suggests mechanisms underlying COVID-19-associated anosmia

“…Normalized gene expression tables were obtained from previous published datasets [51][52][53][54] . For the mouse data sets, the means of the replicates from WOM or OSN were used to calculate Log2 fold changes.…”

“…For the mouse data sets, the means of the replicates from WOM or OSN were used to calculate Log2 fold changes. For the mouse data from Saraiva et al and the primate data sets 52,54 , the normalized counts of the genes of interest from individual replicates were plotted. Below is a table for the detailed sample information.…”

“…It therefore remains unclear whether any cell types in the OE express ACE2, TMPRSS2 or other molecules involved in coronavirus entry, which would render them susceptible to direct infection by CoV-2. To address the hypothesis that CoV-2 causes anosmia through primary effects on the OE, we queried publicly available mouse, nonhuman primate and human RNA sequencing (RNASeq) and scSeq datasets that include definitive OE populations to assess CoV-2-related gene expression 37,46,[48][49][50][51][52][53][54][55] . We also mapped scSeq data across different datasets to compare observed gene expression levels from nasal samples to samples obtained from other airway tissues.…”

Expert Curation of the Human and Mouse Olfactory Receptor Gene Repertoires Identifies Conserved Coding Regions Split Across Two Exons

“…For mouse, we used twelve samples from previous studies (11,19). For human, we combined data from two independent studies (12,20), and sequenced six additional samples to increase the coverage and representation of the OR genes (Methods). We visually examined each of the generated gene models in both species and manually curated them to remove artefacts and errors (Methods).…”

“…Annotation of the human OR gene repertoire has proved more challenging, mostly due to the difficulty in obtaining high-quality olfactory mucosa samples from humans. To date, there are very few studies that have sequenced the transcriptome of human olfactory mucosa samples (12,20). Olender at al.…”