Analysis of Wnt8 for neural posteriorizing factor by identifying Frizzled 8c and Frizzled 9 as functional receptors for Wnt8.
The dorsal ectoderm of vertebrate gastrula is first specified into anterior fate by an activation signal and posteriorized by a graded transforming signal, leading to the formation of forebrain, midbrain, hindbrain and spinal cord along the anteroposterior (A-P) axis. Transplanted non-axial mesoderm rather than axial mesoderm has an ability to transform prospective anterior neural tissue into more posterior fates in zebrafish. Wnt8 is a secreted factor that is expressed in non-axial mesoderm. To investigate whether Wnt8 is the neural posteriorizing factor that acts upon neuroectoderm, we first assigned Frizzled 8c and Frizzled 9 to be functional receptors for Wnt8. We then, transplanted non-axial mesoderm into the embryos in which Wnt8 signaling is cell-autonomously blocked by the dominant-negative form of Wnt8 receptors. Non-axial mesodermal transplants in embryos in which Wnt8 signaling is cell-autonomously blocked induced the posterior neural markers as efficiently as in wild-type embryos, suggesting that Wnt8 signaling is not required in neuroectoderm for posteriorization by non-axial mesoderm. Furthermore, Wnt8 signaling, detected by nuclear localization of beta-catenin, was not activated in the posterior neuroectoderm but confined in marginal non-axial mesoderm. Finally, ubiquitous over-expression of Wnt8 does not expand neural ectoderm of posterior character in the absence of mesoderm or Nodal-dependent co-factors. We thus conclude that other factors from non-axial mesoderm may be required for patterning neuroectoderm along the A-P axis.
Momoi
Akihiro
A
Abteilung für Entwicklungsbiologie, Institut für Biologie I, Universität Freiburg, D-79104 Freiburg, Germany.
Yoda
Hiroki
H
Steinbeisser
Herbert
H
Fagotto
Francois
F
Kondoh
Hisato
H
Kudo
Akira
A
Driever
Wolfgang
W
Furutani-Seiki
Makoto
M
D000595:Amino Acid Sequence; D000818:Animals; D015152:Blotting, Northern; D002467:Cell Nucleus / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D005799:Genes, Dominant; D017403:In Situ Hybridization; D008648:Mesoderm / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D009474:Neurons / Q000378:metabolism*; D010641:Phenotype; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000235:genetics / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000235:genetics / Q000502:physiology*; D017981:Receptors, Neurotransmitter / Q000235:genetics / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D013997:Time Factors; D015534:Trans-Activators / Q000378:metabolism; D051153:Wnt Proteins; D015027:Zebrafish; D029961:Zebrafish Proteins / Q000235:genetics / Q000502:physiology*; D051176:beta Catenin
D003598:Cytoskeletal Proteins; D018076:DNA, Complementary; C498591:Fzd3a protein, zebrafish; D011506:Proteins; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D017981:Receptors, Neurotransmitter; D015534:Trans-Activators; D051153:Wnt Proteins; D029961:Zebrafish Proteins; D051176:beta Catenin; C495269:ctnnb1 protein, zebrafish; C480285:fzd5 protein, zebrafish; C094521:wnt8a protein, zebrafish