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The Roles of the Wnt-Antagonists Axin and Lrp4 during Embryogenesis of the Red Flour Beetle Tribolium castaneum

Department of Genetics, Biological Sciences, University of Rostock, Albert-Einstein-Str. 3, D 18059 Rostock, Germany
Animal Genetics, University of Tübingen, Auf der Morgenstelle 15, D 72076 Tübingen, Germany
Author to whom correspondence should be addressed.
J. Dev. Biol. 2017, 5(4), 10;
Received: 23 August 2017 / Revised: 22 September 2017 / Accepted: 12 October 2017 / Published: 15 October 2017
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In both vertebrates and invertebrates, the Wnt-signaling pathway is essential for numerous processes in embryogenesis and during adult life. Wnt activity is fine-tuned at various levels by the interplay of a number of Wnt-agonists (Wnt ligands, Frizzled-receptors, Lrp5/6 coreceptors) and Wnt-antagonists (among them Axin, Secreted frizzled and Lrp4) to define anterior–posterior polarity of the early embryo and specify cell fate in organogenesis. So far, the functional analysis of Wnt-pathway components in insects has concentrated on the roles of Wnt-agonists and on the Wnt-antagonist Axin. We depict here additional features of the Wnt-antagonist Axin in the flour beetle Tribolium castaneum. We show that Tc-axin is dynamically expressed throughout embryogenesis and confirm its essential role in head development. In addition, we describe an as yet undetected, more extreme Tc-axin RNAi-phenotype, the ectopic formation of posterior abdominal segments in reverse polarity and a second hindgut at the anterior. For the first time, we describe here that an lrp4 ortholog is involved in axis formation in an insect. The Tribolium Lrp4 ortholog is ubiquitously expressed throughout embryogenesis. Its downregulation via maternal RNAi results in the reduction of head structures but not in axis polarity reversal. Furthermore, segmentation is impaired and larvae develop with a severe gap-phenotype. We conclude that, as in vertebrates, Tc-lrp4 functions as a Wnt-inhibitor in Tribolium during various stages of embryogenesis. We discuss the role of both components as negative modulators of Wnt signaling in respect to axis formation and segmentation in Tribolium. View Full-Text
Keywords: Tribolium; Wnt signaling; Wnt-antagonist; Axin; LRP4; AP-polarity; double abdomen Tribolium; Wnt signaling; Wnt-antagonist; Axin; LRP4; AP-polarity; double abdomen

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Prühs, R.; Beermann, A.; Schröder, R. The Roles of the Wnt-Antagonists Axin and Lrp4 during Embryogenesis of the Red Flour Beetle Tribolium castaneum. J. Dev. Biol. 2017, 5, 10.

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J. Dev. Biol. EISSN 2221-3759 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
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