Transcript Early Development of Amphibians

Early Development
Amphibians
Cleavage in a frog
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Describe the progression of events.
Gastrulation in Xenopus
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What have fate maps
told us about tissue
origins?
Gastrulation in Xenopus
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What are VegT and
Vg1 and what
influcence do they
have?
Gastrulation in Xenopus
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What type of cell
movement initiates
gastrulation?
Gastrulation in Xenopus
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What happens next?
Gastrulation in Xenopus
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What happens at the mid-blastula transition
in preparation for gastrulation?
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How is dorsal-ventral axis established?
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What happens if cortical rotation is
blocked?
Gastrulation in Xenopus
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How did Gimlich and Gerhart demonstrate that
certain cells were responsible for inducing dorsal
lip formation?
Gastrulation in Xenopus
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What appears to be the major factor directing
movement of cells into embryo?
Gastrulation in Xenopus
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What other cell movements occur?
Gastrulation in Xenopus
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What two factors appear to drive
convergent extension?
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adhesion proteins paraxial and axial
protocadherin are expressed
changes in calcium concentrations
Gastrulation in Xenopus
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At what point in
gatrulation do
notocordal cells
become distinct?
Gastrulation in Xenopus
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What mechanism appears to be responsible for
epiboly of the ectoderm?
Axis Formation
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How did Hans
Spemann first
demonstrate the
importance of the grey
crescent?
Axis Formation
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What did Spemann do
to demonstrate
changes in cell
potency during
gastrulation?
Axis Formation
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What classic
experiment was done
by Spemann and
Mangold that led to
the concept of the
organizer?
Axis Formation
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How did work of
Nieuwkoop and
Nakamura contribute
to an understanding of
how the “organizer”
worked?
Axis Formation
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What is the
Nieuwkoop center?
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How is it formed?
Axis Formation
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What is involved in the mechanism of
induction of mesoderm by endoderm?
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What appears to be the role of β-catenin?
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What is the connection between β-catenin
and glycogen synthase kinase – 3 (GSK3)?
Axis Formation
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How does β-catenin become concentrated in
dorsal cells of embryo?
Axis Formation
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How does β-catenin
contribute to formation
of the organizer?
Axis Formation
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What model was
developed by Agius to
explain mesodermal
induction?
The Organizer
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What are the four major functions of this
tissue?
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differentiate into dorsal mesoderm
induce formation of paraxial mesoderm
induce formation of neural tube
initiate gastrulation movements
The Organizer
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What is the role of the goosecoid gene?
The Organizer
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How does the
organizer actually
induce formation of
neural tissue?
The Organizer
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What are the proteins
secreted by the
organizer?
The Organizer
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What can the secreted
protein noggin do?
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What other proteins
exhibit similar effects?
The Organizer
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What are some of the
important effects of
BMP-4?
The Organizer
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What are the functions of the diffusable
proteins cerberus, dickkopf and Frzb?
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How do these proteins work?
The Organizer
The Organizer
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Why is neurogenin so
important?
Induction
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How did Otto Mangold demonstrate the regional
specificity of neural induction?
Induction
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Toivonen and Saxen postulated two
gradients in amphibian embryos
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dorsal gradient – “neuralizing” activity
caudal gradient – “posteriorizing” activity
What is the primary protein involved in
posteriorizing the neural tube?
Induction
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What positive signal
promotes anterior
head development?
Left-Right Axis
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What appears to be
major event in leftright axis formation in
Xenopus?