Cellular Communication and Mesoderm Induction Flashcards
What is juxtacrine signalling?
Communication between two cells that are touching
What is bilateria life?
They have bilateral symmetry
Do all bilateria have bilateral symmetry all their life?
No starfish lose it but all have it as larvae
What is radiata life?
Not bilateral at any stage of their life, less complex than bilateria
Give an example of a radiata organism?
A jellyfish
What is Porifera life?
The least complex compared to radiata and bilateria
Give an example of a proifera organism?
Sponge
What are the three germ layers of bilateria?
Ectoderm, endoderm and mesoderm
What is ectoderm?
The skin and nervous system
What is endoderm
The mouth to anus tube down the middle (the gut)
What is mesoderm?
The skeleton, blood, kidney and heart (everything in between)
What kind of animals dont have mesoderm?
Simple ones
What does tripoblastic mean?
All three germ layers
What kind of axes do bilateria organisms have?
A anterior-posterior axis and a doso-ventral axis
What are some examples of bilateria?
Humans, frogs, flies, worms
What kind of axis do radiata organisms have?
One axis - the oral/aboval axis (one orfice for food and poop)
What does dipoblastic mean?
Two germ layers - ecto and endo - no mesoderm
What does monoblastic mean?
One germ layer - ecto
What can be said about the tissues of porifera life?
No true tissues
Evolution of which layer allowed more complex animals to form?
Mesoderm (the one missing from radiata compared to bilateria)
What 3 things about xenopus laevis eggs that make them good for studying embryogensis?
- They are big
- Laid and develop outside the body
- Large so make good amounts of proteins
What defines the axis in a xenopus egg?
They factors (proteins and mRNAs) persent in different areas of the cytoplasm
What pole of the xenopus egg is more dense with the local factors?
The animal pole
What kind of animals are the animal and vegetal pole specific to?
Amphibians
What causes the development of the animal pole?
The point of sperm entry
What would have to be present in order for the sperm to cause the formation of the animal pole?
A receptor for the sperm that allows interactions between speicifc proteins on the animal pole membrane with the sperm
What can be seen in the 32-cell blastula of the xenopus?
The cytoplasm that was present in the 1 cell is localised into the 32 cells and can tell because of their colour
What would you call cells you remove from the 32-cell blastula?
Explants
What happens to explants?
They undergo several cell divisions in culturew
What do cells that have the animal pole cytoplasm go on to make?
Ectoderm (skin cells)
Whar do cells that have the vegetal pole cytoplasm go on to make?
Endoderm (gut)
What is decided at the 32 cell stage and what is not decided?
If the cells are ectoderm or endoderm but no mesoderm has been decided yet
What do you get from an explant of a late stage blastula?
Mesoderm development
What axes can be seen to develop in the late stage embryo?
The dorsal ventral axis
What happens if you take different explants across the cell
You get different subsets of mesoderms
What defines the dorsal ventral axis in the later stage blastula?
the different subsets of mesoderm
What mesoderm defines the dorsal side?
Notochord and somites
What mesoderm defines the ventral side?
Mesenchyme and blood
What is the difference between fate and specification?
Let the cells develop in situ = fate, taking them out and seeing how they develop = specification
If part of the cell develops different insitu (fate) compared to as an explant (specification) what does this tell you?
There must be something telling it do become the fate and if you remove it you lose the signal and therefore it doesnt become it
What happens if you put endoderm and ectoderm near each other?
The cells of the ectoderm that are closest to the endoderm make mesoderm
If the cells of the ectoderm make the mesoderm where is the signal coming from?
The endoderm
What happens if you place ventral endoderm with ectoderm?
It makes notochord and muscle
What happens if you place dorsal endoderm with ectoderm?
The ectoderm makes blood and other tissues
What does the difference in ventral and dorsal endoderm changing the ectoderm tell you?
The signal being sent by the endoderm is different from dorsal to ventral
What niewkoop?
fuck knows
Sum up the example of cell communication in development?
The inductive signal originates in the endoderm and is recieved by the adjacent ectoderm which then becomes mesoderm but the type of mesoderm depends on what part of the endoderm the inductive signal is being trasmitted from (will be different along the dorsal ventral axis)
Where is B-Catenin found?
In the dorsal end of the blastula
What does B-catenin do?
It interacts with TCF/LEF transcrption factors to regulate gene expression
What happens if you inject B-atenin in the ventral side of the blastula?
A second dorsal side will form
What is Veg-t?
A transcription factor found in the vegetal end
What does the cross-over between B-catenin and Veg-T regulate?
Nodal related proteins
What are nodal related proteins?
TGF-B family small protein signals
How are nodal related proteins involved in mesoderm induction?
Different levels of nodal related proteins (caused by the gradient between B-catenin and Veg-T) leads to different levels of nodal signals which means there is a different outcome in what mesoderm is made
