Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Nieuwkoop`s Center
Document related concepts
Transcript
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) • Secondary neural tube forms from recruited host cells • Donor lip cells organize host cells Mesoderm Induced by Vegetal Cells Nieuwkoop’s Experiment Nieuwkoop’s Center Rescues Dorsal Axis & Duplicates Axis in Wild-type Inducing Centers in the Blastula “Spemann” (General) Fate Map of Organizer and Nieuwkoop’s Center Molecular Mechanism of Dorsal Specification VegT, Vg1, Xnr’s mRNAs VegT, Vg1 VegT, Vg1 Accumulation of b-catenin in Dorsal Nuclei V D Dorsal view b-catenin Ventral view Stimulating b-catenin Expression Duplicates Axis Injection of wnt 1 into ventral vegetal (C4) duplicates axes Ventral expression of dominant negative GSK-3 duplicates axes siamois Mis-Expression of Int1 Oncogene Duplicates Axes Int 1 is gene at site of MMLV integration. Identified by H. Varmus McMahon & Moon, 1989 Neural tubes Dominant Negative GSK3 Duplicates Axes Wnt Proteins Not Expressed on Dorsal Side!!! What The… Wnt 8 Some Wnt proteins expressed in the ventral mesoderm and ectoderm Dorsal Blastopore Lip VegT Necessary for Endoderm 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. Cooperation of Vg1, VegT & b-catenin siamois Xbra & Gsc Xbra General Mesoderm Markers D Xenopus brachyury (Xbra) vegetal view 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. Smads and Siamois Specify Nieuwkoop Center Vg1 ligand
