title: Retinoic acid and Wnt/beta-catenin have complementary roles in anterior/posterior patterning embryos of the basal chordate amphioxus.
abstract: A role for Wnt/beta-catenin signaling in axial patterning has been demonstrated in animals as basal as cnidarians, while roles in axial patterning for retinoic acid (RA) probably evolved in the deuterostomes and may be chordate-specific. In vertebrates, these two pathways interact both directly and indirectly. To investigate the evolutionary origins of interactions between these two pathways, we manipulated Wnt/beta-catenin and RA signaling in the basal chordate amphioxus during the gastrula stage, which is the RA-sensitive period for anterior/posterior (A/P) patterning. The results show that Wnt/beta-catenin and RA signaling have distinctly different roles in patterning the A/P axis of the amphioxus gastrula. Wnt/beta-catenin specifies the identity of the ends of the embryo (high Wnt = posterior; low Wnt = anterior) but not intervening positions. Thus, upregulation of Wnt/beta-catenin signaling induces ectopic expression of posterior markers at the anterior tip of the embryo. In contrast, RA specifies position along the A/P axis, but not the identity of the ends of the embryo-increased RA signaling strongly affects the domains of Hox expression along the A/P axis but has little or no effect on the expression of either anterior or posterior markers. Although the two pathways may both influence such things as specification of neuronal identity, interactions between them in A/P patterning appear to be minimal.
authors.affiliation: Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093-0202, USA.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Onai
authors.forename: Hsiu-Chin
authors.initials: HC
authors.lastname: Lin
authors.forename: Michael
authors.initials: M
authors.lastname: Schubert
authors.forename: Demian
authors.initials: D
authors.lastname: Koop
authors.forename: Peter W
authors.initials: PW
authors.lastname: Osborne
authors.forename: Susana
authors.initials: S
authors.lastname: Alvarez
authors.forename: Rosana
authors.initials: R
authors.lastname: Alvarez
authors.forename: Nicholas D
authors.initials: ND
authors.lastname: Holland
authors.forename: Linda Z
authors.initials: LZ
authors.lastname: Holland
mesh_terms: D000818:Animals; D005075:Biological Evolution; D015415:Biomarkers / Q000378:metabolism; D019521:Body Patterning / Q000502:physiology*; D043344:Chordata / Q000145:classification / Q000196:embryology* / Q000378:metabolism*; D005326:Fetal Proteins / Q000235:genetics / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D010802:Phylogeny; D015398:Signal Transduction / Q000502:physiology*; D020825:T-Box Domain Proteins / Q000235:genetics / Q000378:metabolism; D051820:TCF Transcription Factors / Q000235:genetics / Q000378:metabolism; D014212:Tretinoin / Q000378:metabolism*; D051153:Wnt Proteins / Q000235:genetics / Q000378:metabolism*; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism*; D000098908:Brachyury Protein
chemical_list: D015415:Biomarkers; D005326:Fetal Proteins; D018398:Homeodomain Proteins; D020825:T-Box Domain Proteins; D051820:TCF Transcription Factors; D014212:Tretinoin; D051153:Wnt Proteins; D051176:beta Catenin; D000098908:Brachyury Protein