The Expansion of House Mouse Major Urinary Protein Genes Probably Did Not Facilitate Commensalism with Humans

Mouse wild-derived strains (WDS) combine the advantages of classical laboratory stocks and wild animals, and thus appear as promising tools for diverse biomedical and evolutionary studies. We employed 18 WDS representing three non-synanthropic species (Mus spretus, M. spicilegus, and M. macedonicus) and three house mouse subspecies (M. musculus musculus, M. m. domesticus, M. m. castaneus) which are all important human commensals to explore whether the number of major urinary protein (MUP) genes and their final protein levels in the urine are correlated with the level of commensalism. Contrary to expectations, MUP copy number (CN) and protein excretion in the strains derived from M. m. castaneus, which is supposed to be the strongest commensal, were not significantly different from the non-commensal species. Regardless of an overall tendency for higher MUP amounts in taxa with higher CN, there is no significant correlation at the strain level. Our study thus suggests that the expansion of the Mup cluster, which appeared before the house mouse diversification, is unlikely to facilitate commensalism with humans in the three house mouse subspecies. Finally, we found considerable variation among con(sub)specific WDS, warning against generalisations of results based on a few strains.