Direct regulation of the Xenopus engrailed-2 promoter by the Wnt signaling pathway, and a molecular screen for Wnt-responsive genes, confirm a role for Wnt signaling during neural patterning in Xenopus

Mech Dev. 1999 Sep;87(1-2):21-32. doi: 10.1016/s0925-4773(99)00136-7.

Abstract

The co-activation of Wnt signaling and concomitant inhibition of BMP signaling has previously been implicated in vertebrate neural patterning, as evidenced by the combinatorial induction of engrailed-2 and krox-20 in Xenopus. However, screens have not previously been conducted to identify additional potential target genes. Using a PCR-based screening method we determined that XA-1, xCRISP, UVS.2, two UVS.2-related genes, and xONR1 are induced in response to Xwnt-3a and a BMP-antagonist, noggin. Two additional genes, connexin 30 and retinoic acid receptor gamma were induced by Xwnt-3a alone. To determine whether any of the induced genes are direct targets of Wnt signaling, we focussed on engrailed-2. In the present study we show that the Xenopus engrailed-2 promoter contains three consensus binding sites for LEF/TCF, which are HMG box transcription factors which bind to beta-catenin in response to activation of the Wnt- 1 signaling pathway. An engrailed-2 promoter luciferase reporter construct containing these LEF/TCF sites is induced in embryo explant assays by the combination of Xwnt-3a or beta-catenin and noggin. These LEF/TCF sites are required for expression of engrailed-2, as a dominant negative Xtcf-3 blocks expression of endogenous engrailed-2 as well as expression of the reporter construct. Moreover, mutation of these three LEF/TCF sites abrogates expression of the reporter construct in response to noggin and Xwnt-3a or beta-catenin. We conclude that the engrailed-2 gene is a direct target of the Wnt signaling pathway, and that Wnt signaling works with BMP antagonists to regulate gene expression during patterning of the developing nervous system of Xenopus.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Body Patterning / genetics
  • Carrier Proteins
  • Cell Lineage
  • Cytoskeletal Proteins / genetics
  • Cytoskeletal Proteins / metabolism
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism
  • Gene Expression Regulation, Developmental*
  • Genes, Dominant
  • Genes, Reporter
  • HMGB Proteins*
  • Homeodomain Proteins / genetics*
  • Homeodomain Proteins / metabolism
  • Humans
  • Lymphoid Enhancer-Binding Factor 1
  • Nerve Tissue Proteins / genetics*
  • Nerve Tissue Proteins / metabolism
  • Nervous System / embryology
  • Promoter Regions, Genetic*
  • Proteins / metabolism
  • Proto-Oncogene Proteins / genetics*
  • Proto-Oncogene Proteins / metabolism
  • Recombinant Proteins / metabolism
  • Signal Transduction*
  • TCF Transcription Factors
  • Trans-Activators*
  • Transcription Factor 3
  • Transcription Factor 7-Like 1 Protein
  • Transcription Factors / genetics
  • Transcription Factors / metabolism
  • Wnt Proteins
  • Wnt1 Protein
  • Xenopus
  • Xenopus Proteins
  • Zebrafish Proteins*
  • beta Catenin

Substances

  • CTNNB1 protein, Xenopus
  • CTNNB1 protein, human
  • Carrier Proteins
  • Cytoskeletal Proteins
  • DNA-Binding Proteins
  • HMGB Proteins
  • Homeodomain Proteins
  • Lymphoid Enhancer-Binding Factor 1
  • Nerve Tissue Proteins
  • Proteins
  • Proto-Oncogene Proteins
  • Recombinant Proteins
  • TCF Transcription Factors
  • TCF7L1 protein, human
  • Tcf3 protein, Xenopus
  • Trans-Activators
  • Transcription Factor 3
  • Transcription Factor 7-Like 1 Protein
  • Transcription Factors
  • WNT1 protein, Xenopus
  • WNT1 protein, human
  • Wnt Proteins
  • Wnt1 Protein
  • Xenopus Proteins
  • Zebrafish Proteins
  • beta Catenin
  • engrailed 2 protein
  • noggin protein

Associated data

  • GENBANK/AF152960