BIO 302 Study Guide - Final Guide: Regional Differentiation, Wnt Signaling Pathway, Catenin
• If cortical rotation is inhibited, the dorsal side won’t form
What forms first, the organizer or the nieuwkoop center?
• The nieuwkoop center forms first
Figuring out how doral axis gets established in frogs?
• Experiment
o Zap embryos with UV radiation you get no cortical rotation, nor dorsal side ,
which results in the embryo being ventralized.
o If UV radiated embryos are injected with wnt (vertebrate version of wingless,
signaling molecule) mRNA , the mRNA gets translated into wnt protein
o “RESCUES” dorsal development which means ventralized embryo is now able to
make dorsal stratomer (ex. Eyes) due to added signal
o So: wnt signal must be important for dorsal development.
Steps in dorsal specification & mesoderm specification
• ϐ-Catenin + GSK protein distributed throughout egg (animal)
• Maternal factors already in vegetal side of the egg; Veg1 + VegT
• Wnt signaling induced by cortical rotation on the future dorsal side.
o Prevents breakdown of ϐ-catenin dorsally
▪ Β-catenin broken down by GSK
• Wnt signal inhibits GSK so ϐ-catenin no broken down (future dorsal)
Dorsal Axis Induction
Dorsal Side
1. Wnt Signal
2. Blocks Gsk
3. Allows buildup ϐ-catenin buildup
4. ϐ-catenin acts as a transcription factor to induce Nieukoop cetner
Ventral Side
1. No wnt signal
2. Gsk not blocked
3. Gsk breaks down ϐ-catenin
4. No dorsal development ‘
B-catenin acts as a transcription factor to cause expression of “organizer genes”, ex. Siamois
(trx. factor)
Mesoderm Induction:
• Maternal VegT,Veg1 produced in egg; vegetal cytoplasm
o Signals endoderm development
Dorsal Side:
• B-catenin maternally distributed through the egg
• Allow buildup of b-cat dorsally
o
• Activate “dorsal genes
• Overlap of b-cat + veg T/Veg1
• Expr. of siamois in nieuwkoop center
FGF bead induces supernumerary limb bud
find more resources at oneclass.com
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Document Summary
If cortical rotation is inhibited, the dorsal side won"t form. What forms first, the organizer or the nieuwkoop center: the nieuwkoop center forms first. Figuring out how doral axis gets established in frogs: experiment, zap embryos with uv radiation you get no cortical rotation, nor dorsal side , which results in the embryo being ventralized. If uv radiated embryos are injected with wnt (vertebrate version of wingless, signaling molecule) mrna , the mrna gets translated into wnt protein. Rescues dorsal development which means ventralized embryo is now able to make dorsal stratomer (ex. Eyes) due to added signal: so: wnt signal must be important for dorsal development. Dorsal side: wnt signal, blocks gsk, allows buildup -catenin buildup, -catenin acts as a transcription factor to induce nieukoop cetner. Ventral side: no wnt signal, gsk not blocked, gsk breaks down -catenin, no dorsal development . B-catenin acts as a transcription factor to cause expression of organizer genes , ex.
