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Mammalian tears are produced by lacrimal glands to protect eyes and to function in chemical communication and immunity. However, excess tears flow through nasolacrimal ductsto nasal tissues, and via the nasopharyngeal duct to the oral cavity where digestion starts. Tears contain soluble proteins that attack pathogens, as well as proteins from the lipocalin family that – with their capacity to transport volatile organic compounds (VOCs) in their eight-stranded beta barrel – are involved in sexual signalling and may also transport toxic VOCs towards digestion. Therefore, we generated the tear proteome of the wild-living house mouse (Mus musculus musculus) and detected a total of 719 proteins in tears with 20% being sexually dimorphic. Those proteins that showed the most elevated sexual dimorphisms are VOC transporters from the recently discovered odorant binding protein (OBP), and major urinary protein (MUP) families, thus demonstrating that tears have the potential to elicit sex-specific signals in combination with different lipocalins. Moreover, some tear lipocalins are non-dimorphic – with MUP20/Darcin, LCN11, and LCN13 being good examples – thus suggesting that they are involved in other biological processes besides sexual signalling.
This is a submission to PeerJ for review.
Original data from LC-MS/MS (i.e. log2 transformed peak areas, and peptides) and from the RNAseq-based analysis (i.e. Count table).