Unbound MEDLINE

Asymmetrically expressed axin required for anterior development in Tribolium.

Abstract

Canonical Wnt signaling has been implicated in an AP axis polarizing mechanism in most animals, despite limited evidence from arthropods. In the long-germ insect, Drosophila, Wnt signaling is not required for global AP patterning, but in short-germ insects including Tribolium castaneum, loss of Wnt signaling affects development of segments in the growth zone but not those defined in the blastoderm. To determine the effects of ectopic Wnt signaling, we analyzed the expression and function of axin, which encodes a highly conserved negative regulator of the pathway. We found Tc-axin transcripts maternally localized to the anterior pole in freshly laid eggs. Expression spread toward the posterior pole during the early cleavage stages, becoming ubiquitous by the time the germ rudiment formed. Tc-axin RNAi produced progeny phenotypes that ranged from mildly affected embryos with cuticles displaying a graded loss of anterior structures, to defective embryos that condensed at the posterior pole in the absence of serosa. Altered expression domains of several blastodermal markers indicated anterior expansion of posterior fates. Analysis of other canonical Wnt pathway components and the expansion of Tc-caudal expression, a Wnt target, suggest that the effects of Tc-axin depletion are mediated through this pathway and that Wnt signaling must be inhibited for proper anterior development in Tribolium. These studies provide unique evidence that canonical Wnt signaling must be carefully regulated along the AP axis in an arthropod, and support an ancestral role for Wnt activity in defining AP polarity and patterning in metazoan development.

Links

  • PMC Free PDF
  • PMC Free Full Text
  • Publisher Full Text
  • Authors

    Fu J, Posnien N, Bolognesi R, Fischer TD, Rayl P, Oberhofer G, Kitzmann P, Brown SJ, Bucher G

    Institution

    Division of Biology, Kansas State University, Manhattan, KS 66502, USA.

    Source

    Proceedings of the National Academy of Sciences of the United States of America 109:20 2012 May 15 pg 7782-6

    MeSH

    Animals
    Axin Protein
    Body Patterning
    Gene Expression Regulation, Developmental
    Histological Techniques
    Image Processing, Computer-Assisted
    In Situ Hybridization
    RNA Interference
    Tribolium
    Wnt Signaling Pathway

    Pub Type(s)

    Journal Article
    Research Support, N.I.H., Extramural
    Research Support, Non-U.S. Gov't

    Language

    eng

    PubMed ID

    22552230