Volatile signals of the major histocompatibility complex in male mouse urine

Abstract

Variation in the genes of the major histocompatibility complex (MHC) contributes to unique individual odors (odortypes) in mice, as demonstrated by the ability of trained mice in a Y-maze olfactometer to discriminate nearly identical inbred mice that differ genetically only at the MHC (MHC congenic mice), while they cannot distinguish genetically identical inbred mice. Similar distinctions are possible with urine, a substance that is involved in many facets of mouse chemical communication. This paper reports results supporting the hypothesis that the MHC-determined urinary odor is composed of a mixture of volatile carboxylic acids occurring in relative concentrations that are characteristic of the odortype. Y-maze behavioral testing of urine fractions from anion exchange chromatography indicates that volatile acids are necessary and sufficient to convey MHC odortype information. Diethyl ether extracts, which are expected to contain the more volatile, less polar organic acids, were also discriminable in the Y-maze olfactometer. Ether extracts of 12 different urine samples from each of two panels of MHC congenic mice were analyzed by gas chromatography. No compounds unique to urine of either genotype were detected, but compounds did appear to occur in characteristic ratios in most of the samples of each type. Nonparametric statistical analysis of the gas chromatographic data showed that eight of the peaks occurred in significantly different relative concentrations in the congenic samples. One of the peaks was shown to represent phenylacetic acid, which has implications for the mechanism of the MHC specification of odortype.

Olfactory Fingerprints for Major Histocompatibility Complex-Determined Body Odors II: Relationship among Odor Maps, Genetics, Odor Composition, and Behavior

“…Hierarchical cluster analysis is a statistical method for finding relatively homogeneous clusters of cases based on measured characteristics. In both the PCA and hierarchical analysis, the points corresponding to the H-2 b and H-2 k mice formed distinct clusters consistent with previous behavioral, chemical, and f unctional mapping studies (Yamazaki et al, 1990;Singer et al, 1997;Schaefer and Restrepo, 2001b). The two mutant strains (H-2 bm8 and H-2 bm1 ) were associated more closely with H-2 b as would be expected from their genetic relationships and from behavioral studies.…”

“…To explore the relationship between genetics, composition of urine volatiles, and the spatial representation of these complex stimuli, we used as stimuli urine from mice with a single MHC gene difference (isogenic or more specifically mutant) and compared it with urine from mice differing at all the MHC genes (congenic). Individual odor discrimination according to H-2 type is likely to involve the relative amounts of certain volatiles rather than the absolute amount of one or two compounds (Singer et al, 1997). Therefore, to test whether MHC gene differences result in a change in the composition of urine, we asked whether the relative proportion of volatiles of individual samples formed groups reflecting the H-2 type of the donors.…”

“…Methods used for urine sample preparation for gas chromatography were similar to those described in Singer et al (1997). Samples from individual male mice of the four inbred strains (C57BL /6, H-2 b ; B6.AK R, H-2 k ; C57BL /6, H-2 bm8 ; and C57BL /6, H-2 bm1 ) were collected as described previously (Yamazaki et al, 1983(Yamazaki et al, , 1990).…”

“…1, 2) were used to determine the relative pattern of the 41 volatiles for each individual and their respective genetic group. Although it is unknown which, if any, of these distinct compounds are actually used in odor discrimination according to H-2 type, we do know that it is likely to involve the relative amounts of certain volatiles rather than the absolute amount of one or two compounds (Singer et al, 1997). Therefore, we asked whether the relative proportion of volatiles of individual samples formed groups reflecting the H-2 type of the donors.…”

Facts, fallacies, fears, and frustrations with human pheromones

“…Two-thirds of individuals who had the strongest body odors, when evaluated organoleptically, were from one of the above antigenic specificities, suggesting a direct link between body odor intensity and levels of soluble HLA-related proteins. The only study that has examined the structures of immune system-related odorants was performed with rodents (Singer et al, 1997). Data in this publication suggest that in these animals the urinary odorprint is formed by acidic constituents.…”