title: Inhibitory Gli3 activity negatively regulates Wnt/beta-catenin signaling.
abstract: The Hedgehog (Hh) and Wingless (Wnt) families of secreted signaling molecules have key roles in embryonic development and adult tissue homeostasis [1-3]. In the developing neural tube, Wnt and Shh, emanating from dorsal and ventral regions, respectively, have been proposed to govern the proliferation and survival of neural progenitors [4-10]. Surprisingly, Shh is required for the growth and survival of cells in both ventral and dorsal neural tube [11]. Here we demonstrate that inhibition of Shh signaling causes a reduction in Wnt-mediated transcriptional activation. This reduction requires Gli3. Assays in embryos and cell lines indicate that repressor forms of the Hh-regulated transcription factor, Gli3 (Gli3R), which are generated in the absence of Hh signaling, inhibit canonical Wnt signaling. Gli3R acts by antagonizing active forms of the Wnt transcriptional effector, beta-catenin. Consistent with this, Gli3R appears to physically interact with the carboxy-terminal domain of beta-catenin, a region that includes the transactivation domain. These data offer an explanation for the proliferative defects in Shh null embryos and suggest a novel mechanism for crosstalk between the Hh and Wnt pathways.
authors.affiliation: Developmental Neurobiology, National Institute for Medical Research, Mill Hill, London, United Kingdom.
authors.forename: Fausto
authors.initials: F
authors.lastname: Ulloa
authors.forename: Nobue
authors.initials: N
authors.lastname: Itasaki
authors.forename: James
authors.initials: J
authors.lastname: Briscoe
mesh_terms: D000818:Animals; D002642:Chick Embryo; D004622:Embryo, Mammalian / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000378:metabolism; D047108:Embryonic Development; D005786:Gene Expression Regulation; D053823:Hedgehog Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D051741:Kruppel-Like Transcription Factors / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D025941:Protein Interaction Mapping; D015398:Signal Transduction; D051153:Wnt Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D060508:Wnt3 Protein; D014981:Xenopus; D000074290:Zinc Finger Protein Gli3; D051176:beta Catenin / Q000037:antagonists & inhibitors* / Q000378:metabolism
chemical_list: C065683:GLI3 protein, human; C465571:Gli3 protein, mouse; D053823:Hedgehog Proteins; D051741:Kruppel-Like Transcription Factors; D009419:Nerve Tissue Proteins; D051153:Wnt Proteins; D060508:Wnt3 Protein; D000074290:Zinc Finger Protein Gli3; D051176:beta Catenin