title: Mammalian keratin associated proteins (KRTAPs) subgenomes: disentangling hair diversity and adaptation to terrestrial and aquatic environments.
abstract: BACKGROUND
  Adaptation of mammals to terrestrial life was facilitated by the unique vertebrate trait of body hair, which occurs in a range of morphological patterns. Keratin associated proteins (KRTAPs), the major structural hair shaft proteins, are largely responsible for hair variation.
  
  
  RESULTS
  We exhaustively characterized the KRTAP gene family in 22 mammalian genomes, confirming the existence of 30 KRTAP subfamilies evolving at different rates with varying degrees of diversification and homogenization. Within the two major classes of KRTAPs, the high cysteine (HS) subfamily experienced strong concerted evolution, high rates of gene conversion/recombination and high GC content. In contrast, high glycine-tyrosine (HGT) KRTAPs showed evidence of positive selection and low rates of gene conversion/recombination. Species with more hair and of higher complexity tended to have more KRATP genes (gene expansion). The sloth, with long and coarse hair, had the most KRTAP genes (175 with 141 being intact). By contrast, the "hairless" dolphin had 35 KRTAPs and the highest pseudogenization rate (74% relative to the 19% mammalian average). Unique hair-related phenotypes, such as scales (armadillo) and spines (hedgehog), were correlated with changes in KRTAPs. Gene expression variation probably also influences hair diversification patterns, for example human have an identical KRTAP repertoire as apes, but much less hair.
  
  
  CONCLUSIONS
  We hypothesize that differences in KRTAP gene repertoire and gene expression, together with distinct rates of gene conversion/recombination, pseudogenization and positive selection, are likely responsible for micro and macro-phenotypic hair diversification among mammals in response to adaptations to ecological pressures.
authors.forename: Imran
authors.initials: I
authors.lastname: Khan
authors.forename: Emanuel
authors.initials: E
authors.lastname: Maldonado
authors.forename: Vítor
authors.initials: V
authors.lastname: Vasconcelos
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: O'Brien
authors.forename: Warren E
authors.initials: WE
authors.lastname: Johnson
authors.affiliation: CIMAR/CIIMAR, Centro Interdisciplinar de Investigação Marinha e Ambiental, Universidade do Porto, Rua dos Bragas 177, 4050-123 Porto, Portugal. aantunes@ciimar.up.pt.
authors.forename: Agostinho
authors.initials: A
authors.lastname: Antunes
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D001482:Base Composition; D019143:Evolution, Molecular; D005785:Gene Conversion; D015870:Gene Expression; D014644:Genetic Variation; D006197:Hair / Q000378:metabolism*; D007633:Keratins / Q000235:genetics*; D008322:Mammals / Q000235:genetics / Q000378:metabolism*; D005810:Multigene Family; D010802:Phylogeny; D040641:Quantitative Trait Loci; D012641:Selection, Genetic
chemical_list: D007633:Keratins