Glossary of NB503 - Amphibians

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What are two characteristics of cleavage for Amphibian eggs?
Radially symetrical

What does holoblastic mean?
Exhibiting cleavage in which the entire egg separates into individual blastomeres.
What are two functions of the blastocoel?
Blastocoel functions to permit cell migration during gastrulation and to prevent cells from interacting prematurely
In what general area does invagination occur?
Marginal zone - equator.
Where does gastrulation occur?
In or near the grey crescent.
What cells "run the show" during gastrulation?
What is the name of the invagination area where mesoderm are formed and move inward?
dorso blastopore lip
How is the grey crescent formed?
After fertilization, the outer cytoplasm rotates by 30 deg toward the entry point of the sperm. As a result, an area is formed with different biochemical properties.
What is epiboly?
The expansion of one cell sheet over other cells.
What is the name of the cells that indirectly signal ectoderm cells to become neuroectoderm?
dorsal mesoderm
What was the conclusion of Spemann's experiment using a piece of his daughter's hair?
The cresent grey region is critical to the formation of a normal larvae.
What can be said about ectoderm and neuroectoderm cells during early and late stages of gastrulation?
Ectoderm has a conditional specification during early gastrulation and an autonomous specification during late gastrulation.
What can be said about the fate of conditional specification vs autonmous specification cells?
The fate of conditional specification cells is dependent upon other cells, likely near them. The fate of autonomous specification cells is set from the time they are made.
Of all the tissue in early gastrulation, what cells have an autonomous specification?
The tissue within the grey cresent.
What tissue is called the organizer?
dorsal lip tissue
What are two functions of the cells in the dorsal lip tissue?
Organize dorsal ectoderm into a neural tube and transform the flanking mesoderm into the anterior/posterior body axis.
What is induction?
The process by which one embryonic region interacts with a second to influence the differentiation of the second’s.
What was involved in Keller's sandwich experiment? What was concluded.
A sandwich of dorsal blastopore tissue was formed from two animals: ectoderm/mesoderm/mesoderm/ectoderm and grown invitro. Mesoderm tissue was found to extend as it grew.

Conclusion: the dorsal lip is functioning autonomously to create the dorsal mesoderm.
What area controls the Organizer with the result that ectoderm becomes mesoderm?
Nieuwkoop center
After what event is the Nieuwkoop center formed?
30 deg rotation of external cytoplasm after fertilization of the egg.
What protein was moved into the Nieuwkoop center after the 30 deg rotation occured? What does it do?
Dsh - Dishevelled

It inhibits GSK-3 which means that beta-catenin is stable within this region.
If beta-catenin were to be depleted in the Nieuwkoop Center, what would be the result?
The dorsal structure would not be formed.
In what part of the gastrula is there a high concentration of beta-catenin?
Posterior side - high conc.

Anterior side - low conc.
The overlap of high concentrations of what two proteins form the Nieuwkoop center?
beta-cantenin and TGF-beta.
Goosicoid is a protein needed in the Spemann Organizer. What is required to form this protein?
beta-catenin activates the siamois gene -> Siamois protein.

Siamois protein and TGF-beta proteins (Vg1, Nordal) activate the goosecold gene -> goosecold protein.
What would happen if we inject goosecoid into the anterior side of the egg?
Sets up a 2nd dorsal mesoderm area.
What are the five functions of the Spemann Organizer?
1. Ability to become dorsal mesoderm
2. Ability to dorsalize the surrounding mesoderm
3. Ability to dorsalize the ectoderm into neural ectoderm
4. Ability to initiate movements of gastrulation
5. Ability to cause the neural plate to become the neural tube.
What is the name of the first cells to enter involation from the dorsal blastopore lip?
What do the endomesoderm underlie?
The brain and most anterior parts of the head.
What do the newest cells entering at the dorsal mesoderm lip become?
They make up the tail.
What do the ectoderm cells become if the underying dorsal mesoderm cells are remove, i.e. the notochord is removed?
They remain ectoderm and are not changed to neuroectoderm.
What do the ectoderm cells become if they are removed and cultured invitro?
Neuroectoderm cells.
The endoderm normally signals the ectoderm to become what kind of cell?

What protein is generating the signal to become epiderm?

To what family does BMP4 belong?
What three proteins prevent BMP4 from changing ectoderm to epiderm, i.e. they block it?
Noggin, Chordin, Follistatin.
Where are the proteins noggin, chordin, and follistatin located in the highest density?
Dorsal mesoderm.
What prevents anterior head formation in the ectoderm, i.e. stops neurulization (ectoderm -> neuroectoderm)?

Within the name, how is Xenopus identified?

The X.
What is the function of Cerebrus?

What is the method of action?
It causes induction of head structures.

It can bind BMPs and Xwnt8.
What is the function of Frzb?

What is the method of action?
What is the function of Dickkopf?

What is the method of action?

What happens if it is blocked by immunoneutralization?
Allows formation of ????????

Blocks wnt proteins extracellularly.

Embryos with small heads and forebrain are formed.

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