Molecular evolution of the keratin associated protein gene family in mammals, role in the evolution of mammalian hair.
BACKGROUND
Hair is unique to mammals. Keratin associated proteins (KRTAPs), which contain two major groups: high/ultrahigh cysteine and high glycine-tyrosine, are one of the major components of hair and play essential roles in the formation of rigid and resistant hair shafts.


RESULTS
The KRTAP family was identified as being unique to mammals, and near-complete KRTAP gene repertoires for eight mammalian genomes were characterized in this study. An expanded KRTAP gene repertoire was found in rodents. Surprisingly, humans have a similar number of genes as other primates despite the relative hairlessness of humans. We identified several new subfamilies not previously reported in the high/ultrahigh cysteine KRTAP genes. Genes in many subfamilies of the high/ultrahigh cysteine KRTAP genes have evolved by concerted evolution with frequent gene conversion events, yielding a higher GC base content for these gene sequences. In contrast, the high glycine-tyrosine KRTAP genes have evolved more dynamically, with fewer gene conversion events and thus have a lower GC base content, possibly due to positive selection.


CONCLUSIONS
Most of the subfamilies emerged early in the evolution of mammals, thus we propose that the mammalian ancestor should have a diverse KRTAP gene repertoire. We propose that hair content characteristics have evolved and diverged rapidly among mammals because of rapid divergent evolution of KRTAPs between species. In contrast, subfamilies of KRTAP genes have been homogenized within each species due to concerted evolution.
Wu
Dong-Dong
DD
State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, PR China. dongdongw86@yahoo.com.cn
Irwin
David M
DM
Zhang
Ya-Ping
YP
D000595:Amino Acid Sequence; D000818:Animals; D001482:Base Composition; D019143:Evolution, Molecular; D005785:Gene Conversion; D020440:Gene Duplication; D015894:Genome, Human; D006197:Hair; D006801:Humans; D007633:Keratins / Q000235:genetics*; D008322:Mammals / Q000235:genetics*; D005810:Multigene Family; D010802:Phylogeny; D011544:Pseudogenes; D011995:Recombination, Genetic; D013045:Species Specificity
D007633:Keratins