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Flashcards in Frogs - Final Deck (20):

What is some classical evidence that asymmetries exist in the fertilized egg that lead to dorsal development, and the Organizer?

When you split the embryo unequally, the side without a gray crescent forms a belly piece without any anteriorization.


What experimental evidence shows cortical rotation is necessary for asymmetries?

If you UV irradiate an embryo, it cannot undergo cortical rotation. If you simply embed the embryo in wax and perform "tipping" then the embryo is rescued.


How can cortical rotation be seen if the frog does not have a gray crescent?

Nile blue can be used to spot the yolk underneath the cortex.


What cytoskeletal system is responsible for cortical rotation, and what happens when this system is over and under expressed? What chemical is used to over express?

Microtubules are necessary for cortical rotation. When they are under expressed, the embryo forms a belly piece. But over expressed, and they form an excessive anterior head structure without a trunk or tail. D2O is used to over express.


What classical evidence exists to show that dorsal vegetal cells lead to the induction of the Organizer?

An irradiated embryo in injected with Dorsal vegetal cells, and can be rescued/ form an Organizer.


What evidence is there that suggests dorsal endoderm can induce dorsal mesoderm?

When the marginal zone is removed from an embryo, the dorsal endoderm causes the animal cap that is now in contact to become dorsal mesoderm.


What are the steps leading to the formation of the Organizer?

Disheveled combines with GSK-3B, and also aided by XWnt11 maternally to lead to an accumulation of B catenin dorsally. B catenin and TCF combine and activate transcription factors Siamois and Twin. This forms the Nieuwkoop enter, which sends signals to the dorsal mesoderm, causing the formation of the Organizer.


What evidence shows that B catenin is necessary AND sufficient to induce dorsal axial development?

Sufficiency: Injection of B catenin mRNA into VENTRAL vegetal cells caused formation of a secondary axis.
Necessity: B catenin knockdown via morpholinos ventralizes embryos.


Explain the molecular events that lead to dorsal ventral differences in vegetal cells, and the importance of Nodal related proteins.

In vegetal cells, VegT a transcription factor, and Vg1, a TGF beta protein form endoderm, while B catenin is starting to form the Niewkoop center and formation of nodal proteins. These nodal proteins create dorsal vegetal differences in the vegetal cells, which can induce the mesoderm above it differently in a gradient.


Please list the two groups of competing factors with ventral/dorsal differences.

BMP-ventral growth factor is inhibited in dorsal mesoderm by Chordin, and Noggin. XWnt8-ventral growth factor is inhibited in dorsal mesoderm by Frzb, Cerberus, and Dikkopf.


What gastrulation movements of the mesoderm are there, and what kinds of signaling exists in both? What is the result of this induction?

Planar induction occurs at the blastopore lip, and vertical induction occurs as the mesoderm creeps underneath the ectoderm. The result of induction in neural ectoderm.


What is the range of differential molecular signals from anterior to posterior?

Brain in anterior where Wnt inhibitors exist, then Trunk forms spinal cord with BMP inhibitors, then posterior sections are expressing Wnt, FGF, and RA.


List the 5 moving regions that have region specific behaviors.

Animal cap, bottle cells, NIMZ, IMZ, LEM


Animal Cap: What it makes, and movements

makes ectoderm, during gastrulation, undergoes radial intercalation of deep cells into the superficial cell layer, which then undergoes epiboly to cover the surface of the embryo.


Bottle Cells: What it does, and movements

apically constrict at the blastopore lip to help with invagination, and directing involution movements. end up respreading to form the roof of the archenteron.


NIMZ: Definition, end results, gastrulation movements

Region of the external ectoderm that does not involute. Dorsal NIMZ becomes neural ectoderm. Ventral NIMZ becomes epidermis. Gastrulation movements include radial intercalation and convergent extension.


IMZ: Definition, end results, gastrulation movements

Region of the external ectoderm that undergoes involution. Deep cells become organizer, and superficial cells become endoderm roof of the archenteron. Gastrulation movements include rapid and extensive convergent extension.


LEM: Definition, end results, and gastrulation movements

Leading Edge Mesoderm: Interior mesoderm that becomes the head and other migratory mesenchyme. Leads the other mesoderm around the involution. Gastrulation movements include using fibronectin and lamelopodia to crawl on the underside of the blastocoel roof.


Planar Cell Polarity Pathway Necessity

The planar cell polarity pathway helps with convergent extension by causing myosin II protrusions perpendicular to the axis of extension.


Antibody disruption in axolotls of fibronectin

Cause failure of the leading edge mesoderm to migrate along the blastocoel roof. Embryo fails to involute, ectoderm remains wrinkled, and endoderm is not covered.