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Vertebrate Embryonic Patterning 2

Vertebrate Embryonic Patterning 2. Molecular Basis of Nieuwkoop’s Center. Properties of Dorsal Lip Region. Autonomously specified Dorsal lip never respecified by tissue at location of transplantation Donor cells always contribute to notochord (mesoderm)

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Vertebrate Embryonic Patterning 2

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  1. Vertebrate Embryonic Patterning 2 Molecular Basis of Nieuwkoop’s Center

  2. Properties of Dorsal Lip Region • Autonomously specified • Dorsal lip never respecified by tissue at location of transplantation • Donor cells always contribute to notochord (mesoderm) • Secondary neural tube forms from recruited host cells • Donor lip cells organize host cells

  3. Mesoderm Induced by Vegetal Cells

  4. Nieuwkoop’s Experiment

  5. Nieuwkoop’s Center Rescues Dorsal Axis & Duplicates Axis in Wild-type

  6. Inducing Centers in the Blastula “Spemann” (General)

  7. Fate Map of Organizer and Nieuwkoop’s Center

  8. VegT, Vg1, Xnr’s mRNAs VegT, Vg1 VegT, Vg1 Molecular Mechanism of Dorsal Specification

  9. Accumulation of -catenin in Dorsal Nuclei V D Dorsal view b-catenin Ventral view

  10. Stimulating -catenin Expression Duplicates Axis Injection of wnt 1 into ventral vegetal (C4) duplicates axes Ventral expression of dominant negative GSK-3 duplicates axes siamois

  11. Mis-Expression of Int1 Oncogene Duplicates Axes Int 1 is gene at site of MMLV integration. Identified by H. Varmus Neural tubes McMahon & Moon, 1989

  12. Dominant Negative GSK3 Duplicates Axes

  13. Wnt Proteins Not Expressed on Dorsal Side!!! What The… Wnt 8 Some Wnt proteins expressed in the ventral mesoderm and ectoderm Dorsal Blastopore Lip

  14. VegT Necessary for Endoderm

  15. Depletion of Maternal mRNAs Injection of a-sense morpholino oligonucleotide causes degradation of complementary mRNA thereby depleting the oocyte/embryo of that message and the encoded protein. Some maternal proteins may still be present depending on the actual stability of the protein. Technique works best on depleting stored mRNAs which are not translated until after fertilization.

  16. Cooperation of Vg1, VegT & -catenin siamois Xbra & Gsc Xbra

  17. General Mesoderm Markers The initial activation of VegT & Vg1 induces mesoderm. Xbra is expressed throughout the equatorial region prior to gastrulation. Xbra is the founding member of the T-box transcription factor family. D Xenopus brachyury (Xbra) vegetal view

  18. Vg1 ligand Smads and SiamoisSpecify Nieuwkoop Center

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