Identification of major histocompatibility complex-regulated body odorants by statistical analysis of a comparative gas chromatography/mass spectrometry experiment.
This paper examines the application of gas chromatography/mass spectrometry (GC/MS) in a comparative experiment to identify volatile compounds from urine that differ in concentration between two groups of inbred mice. A complex mixture might comprise several hundred or even thousands of volatile compounds. Because their number and location in a chromatogram are generally unknown, and because components overlap in populous chromatograms, the statistical problems offer significant challenges beyond traditional two-group screening procedures. We describe a statistical procedure to compare two-dimensional GC/MS profiles between groups, which entails (1) signal processing, baseline correction, and peak detection in single ion chromatograms; (2) aligning chromatograms in time; (3) normalizing differences in overall signal intensities; and (4) detecting chromatographic regions that differ between groups. In an application to chemosignaling, we detect differences in GC/MS chromatograms of ether-extracted urine collected from two inbred groups of mice that differ only in genes of the major histocompatibility complex (MHC). Several dozen MHC-regulated compounds are found, including two known mouse pheromones, 2,5-dimethylpyrazine and 2-sec-butyl-4,5-dihydrothiazole.
Willse
Alan
A
Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99354, USA. Alan.Willse@pnl.gov
Belcher
Anne M
AM
Preti
George
G
Wahl
Jon H
JH
Thresher
Miranda
M
Yang
Peter
P
Yamazaki
Kunio
K
Beauchamp
Gary K
GK
D000818:Animals; D003627:Data Interpretation, Statistical; D016002:Discriminant Analysis; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D008285:Major Histocompatibility Complex / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009812:Odorants / Q000032:analysis*; D012815:Signal Processing, Computer-Assisted; D014556:Urine / Q000737:chemistry*