Early Development Amphibians
Cleavage in a frog • Describe the progression of events.
Gastrulation in Xenopus • What have fate maps told us about tissue origins?
Gastrulation in Xenopus • What are VegT and Vg1 and what influcence do they have?
Gastrulation in Xenopus • What type of cell movement initiates gastrulation?
Gastrulation in Xenopus • What happens next?
Gastrulation in Xenopus • What happens at the mid-blastula transition in preparation for gastrulation? • How is dorsal-ventral axis established? • What happens if cortical rotation is blocked?
Gastrulation in Xenopus • How did Gimlich and Gerhart demonstrate that certain cells were responsible for inducing dorsal lip formation?
Gastrulation in Xenopus • What appears to be the major factor directing movement of cells into embryo?
Gastrulation in Xenopus • What other cell movements occur?
Gastrulation in Xenopus • What two factors appear to drive convergent extension? • adhesion proteins paraxial and axial protocadherin are expressed • changes in calcium concentrations
Gastrulation in Xenopus • At what point in gatrulation do notocordal cells become distinct?
Gastrulation in Xenopus • What mechanism appears to be responsible for epiboly of the ectoderm?
Axis Formation • How did Hans Spemann first demonstrate the importance of the grey crescent?
Axis Formation • What did Spemann do to demonstrate changes in cell potency during gastrulation?
Axis Formation • What classic experiment was done by Spemann and Mangold that led to the concept of the organizer?
Axis Formation • How did work of Nieuwkoop and Nakamura contribute to an understanding of how the “organizer” worked?
Axis Formation • What is the Nieuwkoop center? • How is it formed?
Axis Formation • What is involved in the mechanism of induction of mesoderm by endoderm? • What appears to be the role of β-catenin? • What is the connection between β-catenin and glycogen synthase kinase – 3 (GSK-3)?
Axis Formation • How does β-catenin become concentrated in dorsal cells of embryo?
Axis Formation • How does β-catenin contribute to formation of the organizer?
Axis Formation • What model was developed by Agius to explain mesodermal induction?
The Organizer • What are the four major functions of this tissue? • differentiate into dorsal mesoderm • induce formation of paraxial mesoderm • induce formation of neural tube • initiate gastrulation movements
The Organizer • What is the role of the goosecoid gene?
The Organizer • How does the organizer actually induce formation of neural tissue?
The Organizer • What are the proteins secreted by the organizer?
The Organizer • What can the secreted protein noggin do? • What other proteins exhibit similar effects?
The Organizer • What are some of the important effects of BMP-4?
The Organizer • What are the functions of the diffusable proteins cerberus, dickkopf and Frzb? • How do these proteins work?
The Organizer • Why is neurogenin so important?
Induction • How did Otto Mangold demonstrate the regional specificity of neural induction?
Induction • Toivonen and Saxen postulated two gradients in amphibian embryos • dorsal gradient – “neuralizing” activity • caudal gradient – “posteriorizing” activity • What is the primary protein involved in posteriorizing the neural tube?
Induction • What positive signal promotes anterior head development?
Left-Right Axis • What appears to be major event in left-right axis formation in Xenopus?