title: Phylogeny and adaptive evolution of the brain-development gene microcephalin (MCPH1) in cetaceans.
abstract: BACKGROUND
  Representatives of Cetacea have the greatest absolute brain size among animals, and the largest relative brain size aside from humans. Despite this, genes implicated in the evolution of large brain size in primates have yet to be surveyed in cetaceans.
  
  
  RESULTS
  We sequenced ~1240 basepairs of the brain development gene microcephalin (MCPH1) in 38 cetacean species. Alignments of these data and a published complete sequence from Tursiops truncatus with primate MCPH1 were utilized in phylogenetic analyses and to estimate ω (rate of nonsynonymous substitution/rate of synonymous substitution) using site and branch models of molecular evolution. We also tested the hypothesis that selection on MCPH1 was correlated with brain size in cetaceans using a continuous regression analysis that accounted for phylogenetic history. Our analyses revealed widespread signals of adaptive evolution in the MCPH1 of Cetacea and in other subclades of Mammalia, however, there was not a significant positive association between ω and brain size within Cetacea.
  
  
  CONCLUSIONS
  In conjunction with a recent study of Primates, we find no evidence to support an association between MCPH1 evolution and the evolution of brain size in highly encephalized mammalian species. Our finding of significant positive selection in MCPH1 may be linked to other functions of the gene.
authors.affiliation: Department of Biology, University of California, Riverside, 92521, USA. mmcgowen@med.wayne.edu
authors.forename: Michael R
authors.initials: MR
authors.lastname: McGowen
authors.forename: Stephen H
authors.initials: SH
authors.lastname: Montgomery
authors.forename: Clay
authors.initials: C
authors.lastname: Clark
authors.forename: John
authors.initials: J
authors.lastname: Gatesy
mesh_terms: D000818:Animals; D005075:Biological Evolution; D001921:Brain / Q000254:growth & development* / Q000378:metabolism; D018797:Cell Cycle Proteins; D002591:Cetacea / Q000145:classification* / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D003598:Cytoskeletal Proteins; D014644:Genetic Variation; D006801:Humans; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000235:genetics* / Q000378:metabolism; D009929:Organ Size; D010802:Phylogeny; D011323:Primates / Q000145:classification / Q000235:genetics
chemical_list: D018797:Cell Cycle Proteins; D003598:Cytoskeletal Proteins; C460645:MCPH1 protein, human; D009419:Nerve Tissue Proteins