title: Antero-posterior tissue polarity links mesoderm convergent extension to axial patterning.
abstract: Remodelling its shape, or morphogenesis, is a fundamental property of living tissue. It underlies much of embryonic development and numerous pathologies. Convergent extension (CE) of the axial mesoderm of vertebrates is an intensively studied model for morphogenetic processes that rely on cell rearrangement. It involves the intercalation of polarized cells perpendicular to the antero-posterior (AP) axis, which narrows and lengthens the tissue. Several genes have been identified that regulate cell behaviour underlying CE in zebrafish and Xenopus. Many of these are homologues of genes that control epithelial planar cell polarity in Drosophila. However, elongation of axial mesoderm must be also coordinated with the pattern of AP tissue specification to generate a normal larval morphology. At present, the long-range control that orients CE with respect to embryonic axes is not understood. Here we show that the chordamesoderm of Xenopus possesses an intrinsic AP polarity that is necessary for CE, functions in parallel to Wnt/planar cell polarity signalling, and determines the direction of tissue elongation. The mechanism that establishes AP polarity involves graded activin-like signalling and directly links mesoderm AP patterning to CE.
authors.affiliation: Department of Zoology, University of Toronto, Toronto, Ontario M5S 3G5, Canada.
authors.forename: Hiromasa
authors.initials: H
authors.lastname: Ninomiya
authors.forename: Richard P
authors.initials: RP
authors.lastname: Elinson
authors.forename: Rudolf
authors.initials: R
authors.lastname: Winklbauer
mesh_terms: D028341:Activins / Q000494:pharmacology; D000818:Animals; D019521:Body Patterning / Q000187:drug effects / Q000502:physiology*; D002454:Cell Differentiation / Q000187:drug effects; D016764:Cell Polarity / Q000187:drug effects; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000187:drug effects / Q000196:embryology / Q000378:metabolism; D066298:In Vitro Techniques; D008648:Mesoderm / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D009672:Notochord / Q000166:cytology / Q000187:drug effects / Q000196:embryology / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D051153:Wnt Proteins; D014981:Xenopus / Q000196:embryology* / Q000235:genetics / Q000378:metabolism
chemical_list: D011518:Proto-Oncogene Proteins; D051153:Wnt Proteins; D028341:Activins