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Genetically-based olfactory signatures persist despite dietary variation.

Kwak J, Willse A, Matsumura K, Curran Opiekun M, Yi W, Preti G, Yamazaki K, Beauchamp GK - PLoS ONE (2008)

Bottom Line: Chemical analyses of urinary volatile organic compounds (VOCs) extracted by solid phase microextraction (SPME) and analyzed by gas chromatography/mass spectrometry (GC/MS) are consistent with this inference.Although diet influenced VOC variation more than MHC, with algorithmic training (supervised classification) MHC types could be accurately discriminated across different diets.Thus, although there are clear diet effects on urinary volatile profiles, they do not obscure MHC effects.

View Article: PubMed Central - PubMed

Affiliation: Monell Chemical Senses Center, Philadelphia, Pennsylvania, USA.

ABSTRACT
Individual mice have a unique odor, or odortype, that facilitates individual recognition. Odortypes, like other phenotypes, can be influenced by genetic and environmental variation. The genetic influence derives in part from genes of the major histocompatibility complex (MHC). A major environmental influence is diet, which could obscure the genetic contribution to odortype. Because odortype stability is a prerequisite for individual recognition under normal behavioral conditions, we investigated whether MHC-determined urinary odortypes of inbred mice can be identified in the face of large diet-induced variation. Mice trained to discriminate urines from panels of mice that differed both in diet and MHC type found the diet odor more salient in generalization trials. Nevertheless, when mice were trained to discriminate mice with only MHC differences (but on the same diet), they recognized the MHC difference when tested with urines from mice on a different diet. This indicates that MHC odor profiles remain despite large dietary variation. Chemical analyses of urinary volatile organic compounds (VOCs) extracted by solid phase microextraction (SPME) and analyzed by gas chromatography/mass spectrometry (GC/MS) are consistent with this inference. Although diet influenced VOC variation more than MHC, with algorithmic training (supervised classification) MHC types could be accurately discriminated across different diets. Thus, although there are clear diet effects on urinary volatile profiles, they do not obscure MHC effects.

Show MeSH
Endogenous compound ranked by their importance in discriminating MHC types across diets.The importance measure is assessed by mean decrease in the Gini index (higher values are more important), a relative measure of group (MHC) differences explained. See the text for details. (T) = tentatively identified from mass spectral data.
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pone-0003591-g003: Endogenous compound ranked by their importance in discriminating MHC types across diets.The importance measure is assessed by mean decrease in the Gini index (higher values are more important), a relative measure of group (MHC) differences explained. See the text for details. (T) = tentatively identified from mass spectral data.

Mentions: The same Random Forest method was used to assess how well MHC types could be discriminated amid varying diets. To mimic the sensor mouse discrimination, we constructed a Random Forest classifier to discriminate MHC types for mice on normal diet, and applied the classification rule to mice on synthetic diet. Then we constructed a Random Forest classifier to discriminate MHC types for mice on synthetic diet, and applied the classification rule to mice on normal diet. Across both test sets (containing 37 samples), 6 errors were made, resulting in an error rate of 16%, significantly better than chance. (Using the entire components we get 7 errors.) This error rate translates into an 84% correct classification, close to the 90% found in mouse behavioral testing (Table 2). Compounds that contribute to this prediction are ranked in Figure 3 according to their relative importance and the distributions of the normalized intensities for the top-ranked compounds affected by MHC types are illustrated in Figure 4. Variability between individual observations is greater than we have seen in previous studies [6], [20], probably because lower concentration of urine was used.


Genetically-based olfactory signatures persist despite dietary variation.

Kwak J, Willse A, Matsumura K, Curran Opiekun M, Yi W, Preti G, Yamazaki K, Beauchamp GK - PLoS ONE (2008)

Endogenous compound ranked by their importance in discriminating MHC types across diets.The importance measure is assessed by mean decrease in the Gini index (higher values are more important), a relative measure of group (MHC) differences explained. See the text for details. (T) = tentatively identified from mass spectral data.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2571990&req=5

pone-0003591-g003: Endogenous compound ranked by their importance in discriminating MHC types across diets.The importance measure is assessed by mean decrease in the Gini index (higher values are more important), a relative measure of group (MHC) differences explained. See the text for details. (T) = tentatively identified from mass spectral data.
Mentions: The same Random Forest method was used to assess how well MHC types could be discriminated amid varying diets. To mimic the sensor mouse discrimination, we constructed a Random Forest classifier to discriminate MHC types for mice on normal diet, and applied the classification rule to mice on synthetic diet. Then we constructed a Random Forest classifier to discriminate MHC types for mice on synthetic diet, and applied the classification rule to mice on normal diet. Across both test sets (containing 37 samples), 6 errors were made, resulting in an error rate of 16%, significantly better than chance. (Using the entire components we get 7 errors.) This error rate translates into an 84% correct classification, close to the 90% found in mouse behavioral testing (Table 2). Compounds that contribute to this prediction are ranked in Figure 3 according to their relative importance and the distributions of the normalized intensities for the top-ranked compounds affected by MHC types are illustrated in Figure 4. Variability between individual observations is greater than we have seen in previous studies [6], [20], probably because lower concentration of urine was used.

Bottom Line: Chemical analyses of urinary volatile organic compounds (VOCs) extracted by solid phase microextraction (SPME) and analyzed by gas chromatography/mass spectrometry (GC/MS) are consistent with this inference.Although diet influenced VOC variation more than MHC, with algorithmic training (supervised classification) MHC types could be accurately discriminated across different diets.Thus, although there are clear diet effects on urinary volatile profiles, they do not obscure MHC effects.

View Article: PubMed Central - PubMed

Affiliation: Monell Chemical Senses Center, Philadelphia, Pennsylvania, USA.

ABSTRACT
Individual mice have a unique odor, or odortype, that facilitates individual recognition. Odortypes, like other phenotypes, can be influenced by genetic and environmental variation. The genetic influence derives in part from genes of the major histocompatibility complex (MHC). A major environmental influence is diet, which could obscure the genetic contribution to odortype. Because odortype stability is a prerequisite for individual recognition under normal behavioral conditions, we investigated whether MHC-determined urinary odortypes of inbred mice can be identified in the face of large diet-induced variation. Mice trained to discriminate urines from panels of mice that differed both in diet and MHC type found the diet odor more salient in generalization trials. Nevertheless, when mice were trained to discriminate mice with only MHC differences (but on the same diet), they recognized the MHC difference when tested with urines from mice on a different diet. This indicates that MHC odor profiles remain despite large dietary variation. Chemical analyses of urinary volatile organic compounds (VOCs) extracted by solid phase microextraction (SPME) and analyzed by gas chromatography/mass spectrometry (GC/MS) are consistent with this inference. Although diet influenced VOC variation more than MHC, with algorithmic training (supervised classification) MHC types could be accurately discriminated across different diets. Thus, although there are clear diet effects on urinary volatile profiles, they do not obscure MHC effects.

Show MeSH