Diverse spatial, temporal, and sexual expression of recently duplicated androgen-binding protein genes in Mus musculus.
BACKGROUND
The genes for salivary androgen-binding protein (ABP) subunits have been evolving rapidly in ancestors of the house mouse Mus musculus, as evidenced both by recent and extensive gene duplication and by high ratios of nonsynonymous to synonymous nucleotide substitution rates. This makes ABP an appropriate model system with which to investigate how recent adaptive evolution of paralogous genes results in functional innovation (neofunctionalization).


RESULTS
It was our goal to find evidence for the expression of as many of the Abp paralogues in the mouse genome as possible. We observed expression of six Abpa paralogues and five Abpbg paralogues in ten glands and other organs located predominantly in the head and neck (olfactory lobe of the brain, three salivary glands, lacrimal gland, Harderian gland, vomeronasal organ, and major olfactory epithelium). These Abp paralogues differed dramatically in their specific expression in these different glands and in their sexual dimorphism of expression. We also studied the appearance of expression in both late-stage embryos and postnatal animals prior to puberty and found significantly different timing of the onset of expression among the various paralogues.


CONCLUSIONS
The multiple changes in the spatial expression profile of these genes resulting in various combinations of expression in glands and other organs in the head and face of the mouse strongly suggest that neofunctionalization of these genes, driven by adaptive evolution, has occurred following duplication. The extensive diversification in expression of this family of proteins provides two lines of evidence for a pheromonal role for ABP: 1) different patterns of Abpa/Abpbg expression in different glands; and 2) sexual dimorphism in the expression of the paralogues in a subset of those glands. These expression patterns differ dramatically among various glands that are located almost exclusively in the head and neck, where the sensory organs are located. Since mice are nocturnal, it is expected that they will make extensive use of olfactory as opposed to visual cues. The glands expressing Abp paralogues produce secretions (lacrimal and salivary) or detect odors (MOE and VNO) and thus it appears highly likely that ABP proteins play a role in olfactory communication.
Laukaitis
Christina M
CM
Department of Biological Sciences, Butler University, 4600 Sunset Ave., Indianapolis, Indiana 46208, USA. cxlaukai@stvincent.org
Dlouhy
Stephen R
SR
Emes
Richard D
RD
Ponting
Chris P
CP
Karn
Robert C
RC
D000595:Amino Acid Sequence; D000727:Androgen-Binding Protein / Q000235:genetics*; D000818:Animals; D001483:Base Sequence; D017931:DNA Primers / Q000737:chemistry; D018076:DNA, Complementary / Q000378:metabolism; D019143:Evolution, Molecular; D020440:Gene Duplication; D015870:Gene Expression; D005786:Gene Expression Regulation; D018507:Gene Expression Regulation, Developmental; D051379:Mice; D008809:Mice, Inbred C3H; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009830:Olfactory Bulb / Q000378:metabolism; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000378:metabolism; D017422:Sequence Analysis, DNA; D012727:Sex Characteristics; D012737:Sex Factors; D013997:Time Factors; D014018:Tissue Distribution
D000727:Androgen-Binding Protein; D017931:DNA Primers; D018076:DNA, Complementary; D012333:RNA, Messenger