Abstract
In spite of abundant evidence that Wnts play essential roles in embryonic induction and patterning, little is known about the expression or activities of Wnt receptors during embryogenesis. The isolation and expression of two maternal Xenopus frizzled genes, Xfrizzled-1 and Xfrizzled-7, is described. It is also demonstrated that both can activate the Wnt/beta-catenin signaling pathway as monitored by the induction of specific target genes. Activation of the beta-Catenin pathway has previously been shown to be necessary and sufficient for specifying the dorsal axis of Xenopus. beta-Catenin is thought to work through the cell-autonomous induction of the homeobox genes siamois and twin, that in turn bind to and activate the promoter of another homeobox gene, goosecoid. However, it was found that the beta-catenin pathway regulated the expression of both endogenous goosecoid, and a goosecoid promoter construct, in a cell non-autonomous manner. These data demonstrate that maternal Frizzleds can activate the Wnt/beta-catenin pathway in Xenopus embryos, and that induction of a known downstream gene can occur in a cell non-autonomous manner.
Publication types
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Amino Acid Sequence
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Animals
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Cell-Free System
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Cells, Cultured
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Cytoskeletal Proteins / physiology*
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DNA Primers / chemistry
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Embryo, Nonmammalian / metabolism*
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Evolution, Molecular
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Female
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Frizzled Receptors
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Gene Expression Regulation, Developmental
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Goosecoid Protein
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Homeodomain Proteins / genetics
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Homeodomain Proteins / metabolism*
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Luciferases / metabolism
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Microinjections
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Microscopy, Confocal
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Molecular Sequence Data
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Proto-Oncogene Proteins / metabolism
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RNA / metabolism
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Receptors, Cell Surface / genetics
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Receptors, Cell Surface / metabolism*
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Receptors, G-Protein-Coupled*
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Receptors, Neurotransmitter / genetics
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Receptors, Neurotransmitter / metabolism*
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Repressor Proteins*
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Reverse Transcriptase Polymerase Chain Reaction
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Sequence Homology, Amino Acid
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Signal Transduction / physiology*
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Supine Position / physiology
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Trans-Activators*
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Transcription Factors*
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Wnt Proteins
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Xenopus Proteins*
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Xenopus laevis / embryology*
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Xenopus laevis / physiology
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Zebrafish Proteins*
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beta Catenin
Substances
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CTNNB1 protein, Xenopus
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Cytoskeletal Proteins
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DNA Primers
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FZD1 protein, Xenopus
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FZD1 protein, human
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Frizzled Receptors
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Fzd7 protein, Xenopus
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Goosecoid Protein
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Homeodomain Proteins
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Proto-Oncogene Proteins
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Receptors, Cell Surface
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Receptors, G-Protein-Coupled
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Receptors, Neurotransmitter
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Repressor Proteins
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Trans-Activators
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Transcription Factors
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Wnt Proteins
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Xenopus Proteins
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Zebrafish Proteins
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beta Catenin
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RNA
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Luciferases