Patterning Flashcards
What organization centre precedes the Spemann Organizer?
The Nieuwkoop centre
The formation of the Niewkoop centre is mediated by (1) signaling
B-catenin
What is secreted by the Nieuwkoop centre to induce formation of the organizer?
BMP
In the pictured experiment (similar to but not the same as the Spemann/Mangold transplantation experiment) when the gastrula dorsal lip is being transplanted into presumed epidermis, what is the key result?
When the dorsal gastrula lip is transplanted at different times, a secondary axis is established, but the dorsal structures that it becomes are different - don’t get an entire head, just get different parts of the head
What information does this experiment tell us? (2)
There must be molecules that act along the A-P axis of the dorsal mesodern in a graded manner, and signals from the underlying mesoderm (archenteron roof) instruct the neural plate in a graded manner
Define the endomesoderm and the utility of this name
It is the tissue that is first involved in the formation of the organizer, and it is called this because it is not fully endoderm, but it is fated to become the most anterior parts of the mesoderm / nervous tissues
What key BMP inhibitor is expressed in the endomesoderm?
Cerberus
What occurs when cerberus is injected into vegetal structures?
Results in ectopic head formation but no secondary axis
What 3 important molecules does cerberus inhibit?
Nodal, BMP4 and Wnt
Where are Nodal, BMP4 and Wnt expressed?
In the anterior mesoderm and endoderm (head-fated region)
Nodal and BMP4 are members of this family of molecules
TGF-B
What are the general steps in the Wnt signaling pathway?
Wnt > frizzled > disheveled > GSK-3 > B-catenin
When Wnt is absent, beta-catenin is…
Degraded
When Wnt is present, beta-catenin is…
Active
How does GSK-3 impact B-catenin functioning
GSK-3 is a kinase, it phosphorylates B-catenin when active (GSK-3 not phosphorylated) and then B-catenin is targeted and degraded by proteasomes
What happens if you knock down cerberus using morpholinos? Why?
Nothing - functionally redundant
What molecules are functionally redundant to cerberus? (2)
Frzb and Dickkopf
Cerberus, Frzb, and Dickkopf are all inhibitors of this molecule
Wnt
What kinds of molecules are cerberus, fzrb and dickkopf?
proteins
When a tissue receives Wnt signals, what kind of neural tissue does this induce?
Induces trunk-like (posterior) fates
Another name for Nodal is…
Xnr3