Expression of major urinary protein genes in the nasal glands associated with general olfaction.

Gene expression of major urinary protein (MUP) mRNAs was examined in the mouse nasal tissue. By polymerase chain reaction, we identified two cDNA segments encoding MUP 4 and MUP 5 genes in the nose. The expression level of both MUP 4 and 5 mRNAs in the nasal tissue was very high and exceeded that of the liver. Liver MUPs are excreted into the urine and are known to play an important role in pheromonal communication. We showed that nose and liver MUPs were composed of different subtypes of MUPs and that nose MUP mRNAs was detected in prepubescent periods when liver MUP mRNAs had not yet been transcripted. In situ hybridization revealed that nose MUP mRNAs are localized in the lateral wall and nasal septum and their expression pattern is identical to that of rat odorant-binding protein (OBP)-I. We also identified cDNA of mouse OBP-II gene from the nasal tissue and showed that the expression pattern of MUP gene was identical to that of OBP-II gene in the nose. These histological data indicate that nose MUPs are favorable for catching odorant molecules rather than pheromones, and may share their function with OBPs.