Abstract
BackgroundHair 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.ResultsThe 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.ConclusionMost 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.
Highlights
IntroductionGene families in which duplications, rate variation and pseudogenization occur frequently are likely involved in functional innovation and adaptation [1]
We have described the near-complete inventories of Keratin associated proteins (KRTAPs) genes from the genomes of human, chimpanzee, and rhesus macaque representing primates, mouse and rat representing rodents, dog representing carnivore, opossum representing marsupial, and platypus as a monotreme, and conducted comprehensive analyses of the evolutionary patterns for this gene family, including phylogenetic classification, and the detection of gene conversion
We have described the near-complete inventories of KRTAP genes in eight mammalian genomes
Summary
Gene families in which duplications, rate variation and pseudogenization occur frequently are likely involved in functional innovation and adaptation [1]. Examples of such gene families are those involved in the perception systems, for example, the odorant receptors [2,3,4], the vomeronasal receptors [5,6,7,8], and the sweet/umami and bitter receptors [9,10,11,12]. BMC Evolutionary Biology 2008, 8:241 http://www.biomedcentral.com/1471-2148/8/241 keratin associated protein (KRTAP) gene family, whose encoded proteins are major components of hair, with the goal of revealing the underlying basis for unique mammalian hair and its phenotypic diversity. Most studies have focused on keratins rather than the keratin associated proteins
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