Data from: Major urinary protein levels are associated with social status and context in mouse social hierarchies

We have previously shown that male mice living in groups of 12 males establish and maintain stable linear social hierarchies with each individual having a defined social rank. However, it is not clear which social cues mice use to signal and recognize their relative social status within their hierarchy. In this study, we investigate how individual social status both in pairs and in groups affects the levels of major urinary proteins (MUPs) and specifically MUP20 in urine. We housed groups of adult outbred CD1 male mice in a complex social environment for three weeks and collected urine samples from all individuals repeatedly. We found that dominant males produce more MUPs than subordinates when housed in pairs and that the production of MUPs and MUP20 is significantly higher in alpha males compared with all other individuals in a social hierarchy. Furthermore, we found that hepatic mRNA expression of Mup3 and Mup20 is significantly higher in alpha males than in subordinate males. We also show that alpha males have lower urinary creatinine levels consistent with these males urinating more than others living in hierarchies. These differences emerged within one week of animals being housed together in social hierarchies. This study demonstrates that as males transition to become alpha males, they undergo physiological changes that contribute to communication of their social status that may have implications for the energetic demands of maintaining dominance.我们此前已证实，群居的12只雄性小鼠可建立并维持稳定的线性社会等级，每只个体均拥有明确的社会位次。然而，小鼠通过何种社会信号来传递并识别其在等级中的相对社会地位，目前仍不明确。本研究旨在探究成对饲养与群居环境下的个体社会地位，如何影响尿液中主要尿蛋白（major urinary proteins，MUPs）尤其是MUP20的表达水平。我们将成年远交系CD1雄性小鼠群饲养于复杂社交环境中为期三周，并反复采集所有个体的尿液样本。研究发现，成对饲养时，优势雄性小鼠的主要尿蛋白表达量高于从属个体；且与社会等级中的其他所有个体相比，阿尔法雄性（alpha males）的主要尿蛋白及MUP20表达量显著更高。此外，我们还发现阿尔法雄性的肝脏Mup3与Mup20的mRNA表达水平显著高于从属雄性。我们同时观察到，阿尔法雄性的尿液肌酐水平更低，这与其在社会等级中排尿频率高于其他个体的现象一致。上述差异在动物群居并建立社会等级后的一周内便已显现。本研究表明，当雄性小鼠转变为阿尔法雄性时，其体内会发生生理变化，这些变化有助于传递其社会地位，这可能对维持优势地位所需的能量需求产生影响。