title: Molecular evolution of mammalian aquaporin-2: further evidence that elephant shrew and aardvark join the paenungulate clade.
abstract: A 328-bp sequence from exon 1 of the gene for aquaporin-2 (AQP2) was compared in 12 mammalian species, representing as many eutherian orders. This sequence encodes the N-terminal half of this kidney-specific water channel protein. Most amino acid replacements, as well as an insertion, have occurred in extracellular loops connecting the transmembrane helices, in agreement with a lower functional importance of these loops. Phylogenetic analyses were performed with parsimony, distance, and maximum-likelihood methods. The AQP2 data set, alone as well as in combination with previously published alpha A-crystallin protein sequences, strongly supports a clade consisting of elephant, hyrax, aardvark, and elephant shrew, reaching bootstrap values of 99%. This finding fully agrees with the only other presently available sequence data sets that include these taxa, those of von Willebrand factor and interphotoreceptor retinoid-binding protein, and suggests that this extended paenungulate clade is one of the most conspicuous superordinal groupings in eutherian phylogeny. Some support was obtained for an artiodactyl/perissodactyl clade, while the grouping of pholidotes with edentates was contradicted.
authors.affiliation: Department of Biochemistry, University of Nijmegen, The Netherlands.
authors.forename: O
authors.initials: O
authors.lastname: Madsen
authors.forename: P M
authors.initials: PM
authors.lastname: Deen
authors.forename: G
authors.initials: G
authors.lastname: Pesole
authors.forename: C
authors.initials: C
authors.lastname: Saccone
authors.forename: W W
authors.initials: WW
authors.lastname: de Jong
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D051399:Aquaporin 2; D051403:Aquaporin 6; D020346:Aquaporins; D001483:Base Sequence; D003459:Crystallins / Q000235:genetics; D019143:Evolution, Molecular; D006801:Humans; D007473:Ion Channels / Q000235:genetics*; D008322:Mammals / Q000145:classification* / Q000235:genetics; D008969:Molecular Sequence Data; D010802:Phylogeny; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D012788:Shrews / Q000145:classification* / Q000235:genetics
chemical_list: C496023:AQP2 protein, human; D051399:Aquaporin 2; D051403:Aquaporin 6; D020346:Aquaporins; D003459:Crystallins; D007473:Ion Channels