title: Parallel genetic origins of pelvic reduction in vertebrates.
abstract: Despite longstanding interest in parallel evolution, little is known about the genes that control similar traits in different lineages of vertebrates. Pelvic reduction in stickleback fish (family Gasterosteidae) provides a striking example of parallel evolution in a genetically tractable system. Previous studies suggest that cis-acting regulatory changes at the Pitx1 locus control pelvic reduction in a population of threespine sticklebacks (Gasterosteus aculeatus). In this study, progeny from intergeneric crosses between pelvic-reduced threespine and ninespine (Pungitius pungitius) sticklebacks also showed severe pelvic reduction, implicating a similar genetic origin for this trait in both genera. Comparative sequencing studies in complete and pelvic-reduced Pungitius revealed no differences in the Pitx1 coding sequences, but Pitx1 expression was absent from the prospective pelvic region of larvae from pelvic-reduced parents. A much more phylogenetically distant example of pelvic reduction, loss of hindlimbs in manatees, shows a similar left-right size bias that is a morphological signature of Pitx1-mediated pelvic reduction in both sticklebacks and mice. These multiple lines of evidence suggest that changes in Pitx1 may represent a key mechanism of morphological evolution in multiple populations, species, and genera of sticklebacks, as well as in distantly related vertebrate lineages.
authors.affiliation: Department of Developmental Biology and Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA 94305.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Shapiro
authors.forename: Michael A
authors.initials: MA
authors.lastname: Bell
authors.forename: David M
authors.initials: DM
authors.lastname: Kingsley
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D005075:Biological Evolution; D017124:Conserved Sequence; D008969:Molecular Sequence Data; D051761:Paired Box Transcription Factors / Q000235:genetics / Q000378:metabolism*; D010388:Pelvis / Q000033:anatomy & histology*; D010641:Phenotype; D023701:Smegmamorpha / Q000033:anatomy & histology* / Q000235:genetics
chemical_list: D051761:Paired Box Transcription Factors; C101485:homeobox protein PITX1