title: The Xenopus homeobox gene pitx3 impinges upon somitogenesis and laterality.
abstract: Pitx3 has been identified as the causative locus in a developmental eye mutation associated with mammalian anterior segment dysgenesis, congenital cataracts, and aphakia. In recent studies of frog eye development we discovered that pitx3 expresses symmetrically in the somites and lateral plate mesoderm and asymmetrically during cardiac and gut looping. We report that disruption of pitx3 activity on one side of an embryo relative to the other, either by over- or underexpression of pitx3, elicits a crooked dorsal axis in embryos that is a consequence of a retarded progression through somitogenesis. Unlike in amniotes, Xenopus somites form as cohorts of presomitic cells that rotate perpendicular to the dorsal axis. Since no vertebral anomalies have been reported in mouse and human Pitx3 mutants, we attempt to distinguish whether the segmentation clock is uniquely affected in frog or if the pitx3 perturbation inhibits the cellular changes that are necessary to rotation of presomitic cells. In Xenopus, pitx3 appears to inhibit the rotation of presomitic cell cohorts and to be necessary to the bilaterally symmetric expression of pitx2 in somites.
authors.affiliation: Biological Science, University of Windsor, 401 Sunset Avenue, Windsor, ON N9B 3P4, Canada.
authors.forename: Cristine
authors.initials: C
authors.lastname: Smoczer
authors.forename: Lara
authors.initials: L
authors.lastname: Hooker
authors.forename: Sarah
authors.initials: S
authors.lastname: Brode
authors.forename: Marian
authors.initials: M
authors.lastname: Wolanski
authors.forename: Farhad
authors.initials: F
authors.lastname: KhosrowShahian
authors.forename: Michael
authors.initials: M
authors.lastname: Crawford
mesh_terms: D000818:Animals; D019521:Body Patterning / Q000235:genetics*; D004625:Embryo, Nonmammalian; D007839:Functional Laterality / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D051379:Mice; D009154:Mutation; D038081:Organogenesis / Q000235:genetics*; D019170:Somites / Q000196:embryology / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D029867:Xenopus Proteins / Q000235:genetics* / Q000378:metabolism; D014982:Xenopus laevis / Q000196:embryology / Q000235:genetics* / Q000378:metabolism
chemical_list: C506549:Pitx3 protein, Xenopus; D014157:Transcription Factors; D029867:Xenopus Proteins