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.