Genes of the major histocompatibility complex (MHC) influence the urinary odors of mice. Behavioral studies have shown 1) that mice differing only at MHC have distinct urinary odors, suggesting an MHC odor phenotype or odortype; 2) that the MHC odortype can be recognized across different (potentially interfering) background strains; and 3) that the MHC odortype is not an additive trait. Very little is known about the odorants underlying this behavioral phenotype. We compared urinary volatile metabolite profiles of two MHC haplotypes (H-2b and H-2k) and their heterozygous cross (H-2b × H-2k) for two different background strains using SPME headspace analysis followed by gas chromatography/mass spectrometry. For a surprisingly large number of compounds an MHC association was found to be moderated by background genotype (i.e., there is a significant MHC × background interaction effect in the statistical model relating genotype to relative compound concentration). A few compounds have an MHC association that is independent of background strain, consistent with MHC discriminations across background strains observed in behavioral experiments. Perhaps more relevant to the role of MHC in social settings where odors are perceived combinatorially, numerous relative ratios between pairs of compounds were found to discriminate MHC types invariant of background type. In addition, a heterozygous effect – where the metabolite expression (concentration) for the heterozygote is more extreme than the expression for either homozygote – was observed for many compounds. The large number of compounds involved as well as the strong background and heterozygous influence suggest a complex (but unknown) mechanism of MHC-related odor expression.
Revised: December 5, 2006 |
Published: December 1, 2006
Citation
Willse A.R., J. Kwak, K. Yamazaki, G. Preti, J.H. Wahl, and G. Beauchamp. 2006.Individual odortypes: Interaction of MHC and background genes.Immunogenetics 58, no. 12:967-982.PNNL-SA-49772.doi:10.1007/s00251-006-0162-x