Sea Urchins Flashcards
Sea Urchin [iso/meso, mero/homo]
isolecithal, holoblastic cleavage
Animal/Vegetable pole
animal = top, vegetal = bottom
Cells are equivalent in their content up until the __ cell stage of the embryo
8 cell stage is no longer equivalent
At what stage do meso, macro, and micromeres appear?
At the 16 cell stage
Oral/Aboral, dorsal/ventral
Oral/ventral, dorsal/aboral
Animal Cells produce what tissue type?
Ectoderm
Veg 1 forms what tissue type?
Base of archenteron and ectoderm
Veg 2 forms what tissue type?
endoderm and secondary mesenchyme
Micromeres form what tissue type?
skeletogenic mesenchyme (spicules)
Hyaline layer
Clear layer surrounding the embryo, but not part of the fertilization envelope
Blastopore
Slight ingression at the vegetal pole
Pluteus
Sea urchin that looks like an easel
What conclusion was made concerning the vegetal half of the embryo?
It has the determinants to create mesoderm and endoderm
What happens when you remove the pigment band?
You lose mesoderm and endoderm.
When transplanting micromeres, what happens?
The micromeres induce endoderm formation and primary mesenchyme bundles.
What molecule seems to be creating induction from micromeres?
Nuclear Beta Catenin
Where is nuclear beta catenin found?
Highest levels in the micromeres , followed by the veg 2 cells.
How is beta catenin regulated?
Quality of disheveled that inhibits its destruction
Where is disheveled usually found?
at the vegetal pole of the egg, and the micromere cortex
Wnt 6
important for endoderm formation by expression of FoxA
Frizzled 7
Important receptor for Beta catenin production in macromeres.
Nodal is part of what family of proteins?
TGF Beta Proteins that involve phosphorylation of Smads and transcription factors.
Nodal is important in determining which orientation?
The left right asymmetry, with more nodal in the oral side first, then the right side. Without nodal, the embryo does not show a bilateral symmetry.
EMT transition occurs with the ___ ___ cells. Cells lose adhesion to ___ and ___, but use adhesion with ___ to pull themselves into the interior.
Primary mesenchymal cells undergo EMT, losing connection with hyaline layer and other cells, but grabbing onto the basal lamina.
Vegetal Plate
Thicker layer of cells at bottom of blastula used to protrude the archenteron.
What morphogenic movement is needed to continue expansion of the archenteron?
Convergent Extension
What shape of cells are needed for primary invagination?
Bottle cells
What evidence is there of convergent extension in the archenteron?
The circumference becomes thinner, and when staining cells, it is clear that they go every other.
What are the names of the extensions protruding from the secondary mesenchyme at the tip of the archenteron?
Filopodia
At what stage is filopodia necessary?
After about a third of the archenteron. This means that the embryo is initially capable of convergent extension on its own, but needs additional help from the secondary mesenchyme filopodia.
Attachment to the hyaline layer is needed for ___
invagination
Attachment to the basal lamina is needed for ___
Proper orientation and movement of the archenteron
Two skeletogenic clusters form on the ___ side of the embryo
Ventral (oral) side
What experiments were done with NiCl2, and what does it tell us about spicule formation?
Experiments were done with all combinations of either hard metal blastulas, or hard metal PMCs. PMC’s are influence to create their patterns by their environments. The healthy PMC in a NiCl blastula was incorrect, but an NiCl PMC in a healthy blastula was fine.
What growth factor in involved in spicule pattern formation?
FGF (fibroblast growth factor)
What happens if you cause a dimple on the side of blastula in order to get the archenteron to attach
Nothing, but if you make the dimple at the top, the archenteron ceases growing as soon as it touches the top.
