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.

25The mammalian olfactory system displays species-specific adaptations to different ecological 26 niches. To investigate the evolutionary dynamics of olfactory sensory neuron (OSN) sub-types 27 across 95 million years of mammalian evolution, we applied RNA-sequencing of whole olfactory 28 mucosa samples from mouse, rat, dog, marmoset, macaque and human. We find that OSN 29 subtypes representative of all known mouse chemosensory receptor gene families are present 30 in all analyzed species. Further, we show that OSN subtypes expressing canonical olfactory 31 receptors (ORs) are distributed across a large dynamic range and that homologous subtypes 32 can be either highly abundant across all species or species/order-specific. Interestingly, highly 33 abundant mouse and human OSN subtypes detect odorants with similar sensory profiles, and 34 sense ecologically relevant odorants, such as mouse semiochemicals or human key food 35 odorants. Taken together, our results allow for a better understanding of the evolution of 36 mammalian olfaction in mammals and provide insights into the possible functions of highly 37 abundant OSN subtypes in mouse and human. 38 39 3 MAIN TEXT 40

Objective Fasting regimens can promote health, mitigate chronic immunological disorders, and improve age-related pathophysiological parameters in animals and humans. Several ongoing clinical trials are using fasting as a potential therapy for various conditions. Fasting alters metabolism by acting as a reset for energy homeostasis, but the molecular mechanisms underlying the beneficial effects of short-term fasting (STF) are not well understood, particularly at the systems or multiorgan level. Methods We performed RNA-sequencing in nine organs from mice fed ad libitum (0 h) or subjected to fasting five times (2–22 h). We applied a combination of multivariate analysis, differential expression analysis, gene ontology, and network analysis for an in-depth understanding of the multiorgan transcriptome. We used literature mining solutions, LitLab™ and Gene Retriever™, to identify the biological and biochemical terms significantly associated with our experimental gene set, which provided additional support and meaning to the experimentally derived gene and inferred protein data. Results We cataloged the transcriptional dynamics within and between organs during STF and discovered differential temporal effects of STF among organs. Using gene ontology enrichment analysis, we identified an organ network sharing 37 common biological pathways perturbed by STF. This network incorporates the brain, liver, interscapular brown adipose tissue, and posterior-subcutaneous white adipose tissue; hence, we named it the brain-liver-fats organ network. Using Reactome pathways analysis, we identified the immune system, dominated by T cell regulation processes, as a central and prominent target of systemic modulations during STF in this organ network. The changes we identified in specific immune components point to the priming of adaptive immunity and parallel the fine-tuning of innate immune signaling. Conclusions Our study provides a comprehensive multiorgan transcriptomic profiling of mice subjected to multiple periods of STF and provides new insights into the molecular modulators involved in the systemic immunotranscriptomic changes that occur during short-term energy loss.

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Different fasting regiments are known to promote health, and chronic immunological disorders and mitigate age-related pathophysiological parameters in animals and humans. Indeed, several clinicals trials are currently ongoing using fasting as a potential therapy for a wide range of conditions. Fasting alters metabolism by acting as a reset for energy homeostasis, but the molecular mechanisms underlying the beneficial effects of short-term fasting (STF) are still not-well understood, particularly at a systems/multiorgan level. We investigated the dynamic gene expression patterns associated with periods of STF in nine different mouse organs. First, we identified both unique and shared transcriptional signatures at the organ and systemic levels. Second, we discovered differential temporal effects of STF among organs. Third, using gene ontology enrichment analysis, we identified an organ network, formed by the 63 common biological pathways perturbed by STF. This network incorporates the brain, liver, interscapular brown, and perigonadal white adipose tissue, hence we name it the brain-liver-fats organ network. Fourth, we identified that the immune system, dominated by T cell regulation processes, is a central and prominent target of systemic modulations during short-term energy loss in this organ network. The changes we identified in specific immune components point to the priming of adaptive immunity and parallel the fine-tuning of innate immune signaling. In conclusion, our study provides a comprehensive multi-organ transcriptomic profiling of mice subjected to multiple periods of STF and added new insights into the molecular modulators involved in the systemic immuno-transcriptomic changes that occur during short-term energy loss.