Abstract
Chemical communication is mediated by sex-biased signals abundantly present in the urine, saliva and tears. Because most studies concentrated on the urinary signals, we aimed to determine the saliva proteome in wild Mus musculus musculus, to extend the knowledge on potential roles of saliva in chemical communication. We performed the gel-free quantitative LC-MS/MS analyses of saliva and identified 633 proteins with 134 (21%) of them being sexually dimorphic. They include proteins that protect and transport volatile organic compounds in their beta barrel including LCN lipocalins, major urinary proteins (MUPs), and odorant binding proteins (OBPs). To our surprise, the saliva proteome contains one MUP that is female biased (MUP8) and the two protein pheromones MUP20 (or ‘Darcin’) and ESP1 in individuals of both sex. Thus, contrary to previous assumptions, our findings reveal that these proteins cannot function as male-unique signals. Our study also demonstrates that many olfactory proteins (e.g. LCNs, and OBPs) are not expressed by submandibular glands but are produced elsewhere–in nasal and lacrimal tissues, and potentially also in other oro-facial glands. We have also detected abundant proteins that are involved in wound healing, immune and non-immune responses to pathogens, thus corroborating that saliva has important protective roles.
Highlights
The sequence of the mouse genome provided a tool to study blueprints for all RNAs and proteins in mice[1]
We have provided evidence that odorant binding protein genes (Obp) transcripts are co-expressed in combination with other lipocalin transcripts, presumably to widen the spectrum of ligands that odorant binding proteins (OBPs), major urinary proteins (MUPs), and LCN proteins may sequester and transport[31]
Because Power Law Global Error Model (PLGEM) can only be fitted on a set of replicates of a same experimental condition we have done this for female data, Fig. 1b
Summary
The sequence of the mouse genome provided a tool to study blueprints for all RNAs and proteins in mice[1]. Laboratory mice have been widely and successfully used as experimental organisms in studies of biomarkers of physiological states[2] and of human pathological conditions, they may be less suitable to study chemical communication, a process which is driven by sexual selection This is due to the differential contribution of blocks of genes from the two house-mouse subspecies M. m. VOCs are slowly released from different urinary MUPs, and have been proposed to function in a variety of social signals, including identity, territorial marking, mate choice etc.[3,12,13,14]. Lipocalins and their specific ligands together form a signal[15]. MUPs have been reported in several tissues other than the liver including salivary glands, olfactory/vomeronasal epithelia, and nasal-associated lymphoid tissues[2,8,29,30,31], but their functions are not yet fully understood
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