Rapid bursts of androgen-binding protein (Abp) gene duplication occurred independently in diverse mammals.
BACKGROUND
The draft mouse (Mus musculus) genome sequence revealed an unexpected proliferation of gene duplicates encoding a family of secretoglobin proteins including the androgen-binding protein (ABP) alpha, beta and gamma subunits. Further investigation of 14 alpha-like (Abpa) and 13 beta- or gamma-like (Abpbg) undisrupted gene sequences revealed a rich diversity of developmental stage-, sex- and tissue-specific expression. Despite these studies, our understanding of the evolution of this gene family remains incomplete. Questions arise from imperfections in the initial mouse genome assembly and a dearth of information about the gene family structure in other rodents and mammals.


RESULTS
Here, we interrogate the latest 'finished' mouse (Mus musculus) genome sequence assembly to show that the Abp gene repertoire is, in fact, twice as large as reported previously, with 30 Abpa and 34 Abpbg genes and pseudogenes. All of these have arisen since the last common ancestor with rat (Rattus norvegicus). We then demonstrate, by sequencing homologs from species within the Mus genus, that this burst of gene duplication occurred very recently, within the past seven million years. Finally, we survey Abp orthologs in genomes from across the mammalian clade and show that bursts of Abp gene duplications are not specific to the murid rodents; they also occurred recently in the lagomorph (rabbit, Oryctolagus cuniculus) and ruminant (cattle, Bos taurus) lineages, although not in other mammalian taxa.


CONCLUSIONS
We conclude that Abp genes have undergone repeated bursts of gene duplication and adaptive sequence diversification driven by these genes' participation in chemosensation and/or sexual identification.
Laukaitis
Christina M
CM
Department of Medical Genetics, University of Washington, Seattle, USA and Division of Human Biology, Fred Hutchinson CancerResearch Center, Seattle, USA. claukai@u.washington.edu
Heger
Andreas
A
Blakley
Tyler D
TD
Munclinger
Pavel
P
Ponting
Chris P
CP
Karn
Robert C
RC
D000595:Amino Acid Sequence; D000727:Androgen-Binding Protein / Q000235:genetics*; D000818:Animals; D015139:Blotting, Southern; D019143:Evolution, Molecular; D020440:Gene Duplication; D006801:Humans; D008322:Mammals / Q000235:genetics*; D051379:Mice; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D013045:Species Specificity
D000727:Androgen-Binding Protein