Many MUPs expressed by wild mice

Pes, D., Robertson, D.H.L., Hurst, J.L.., Gaskell, S.J. & Beynon, R.J. (1999) How many Major Urinary Proteins are produced by the house mouse Mus domesticus? in "Chemical Signals in Vertebrates" (R.E. Johnston, D. Müller-Schwarze and P.W.Sorensen eds) Plenum Press 149-161

The major urinary proteins (MUPs) are secreted abundantly into mouse urine as a normal condition. MUPs are thought to be involved in olfactory communication as their distinctive barrel shape allows them to bind two semiochemical molecules. Production of MUPs results from simultaneous expression of a number of closely related MUP genes; the mature proteins therefore have heterogeneous amino acid sequences. Whilst this heterogeneity has been characterised in inbred mice, little is known about the heterogeneity of MUPs in wild mice. No function has ever been ascribed to MUP heterogeneity.
     In this study, the molecular mass and net charge of MUPs from six wild mice, taken from two separate populations, have been determined by electrospray ionization mass spectrometry and anion exchange chromatography respectively. This method of analysis uniquely identifies individual MUPs and has allowed an accurate determination of the number of different MUPs produced by these animals. In this limited sample, the number is much greater than previously observed in inbred mice. The results are discussed both in terms of the total number of MUPs characterised and the variation in heterogeneity between individual animals and populations.