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.

既往研究表明，每群12只雄性小鼠群居时，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地位。然而，目前尚不明确小鼠在其社会等级体系中，依靠何种社会信号来传递并识别彼此的相对社会地位。本研究旨在探究成对饲养与群居环境下，个体的社会地位如何影响尿液中的主要尿蛋白（major urinary proteins, MUPs），尤其是MUP20的含量。我们将成年远交系CD1雄性小鼠饲养于复杂社会环境中，为期三周，并对所有个体反复采集尿液样本。研究发现，成对饲养时优势雄性的MUPs含量高于从属个体；而在社会等级体系中，阿尔法雄性的MUPs与MUP20含量显著高于其他所有个体。此外，我们还观察到阿尔法雄性肝脏中Mup3与Mup20的mRNA表达量显著高于从属雄性。同时，阿尔法雄性的尿液肌酐水平更低，这与其在等级群体中的排尿频次高于其他个体的现象相符。上述差异在动物被纳入社会等级群体饲养后的一周内即可显现。本研究表明，当雄性小鼠晋升为阿尔法雄性时，其体内会发生一系列生理变化，这些变化有助于传递其社会地位信息，这可能对维持统治地位所需的能量代谢需求具有重要意义。