Communication Between Cells Flashcards
What is the body plan of C.elegans?
Ectoderm (skin aroud the outside) followed by mesoderm (body wall, muscle) then endoderm (gut) in the middle
Where are the gonads found in c.elegans?
In the space between the body wall and the intestine
How are the neurons of c.elegans positions?
In a nerve ring
What is useful about the c.elegans embryo?
It is transparent throught embryogenesis so can follow and map cell divisions
How many somatic nuclei are in the adult hermaphrodite?
959
How many somatic nuclei does the adult male have?
1031
Why is mapping very accurate in c.elegans?
Because is it a largely invariant process
What kind of signalling is involved in that of the c.elegans gonad?
Juxtacrine
What are the four cells of the L1 gonad?
Z1-4
What do Z2 and Z3 make?
The germline
What do Z1 and Z4 make?
The somatic tissue of the gonad
What cells are present in the L2 gonad?
The Z2 and Z3 for the germline and 12 somatic cells including z1ppp and z4aaa
What do z1ppp and z4aaa differentiate into?
Anchor and ventral uterine cells (either has the ability to make each kind but only one of each kind is made)
What happens if you leave only z1ppp or z4aaa and kill all other cells?
Ac always forms
What happens if you kill only z1ppp or z4aaa and leave all other cells?
Ac always forms
What happens if you leave z1ppp and z4aaa and kill all other cells?
Ac and Vu are formed
What does the experiment of z1ppp and z4aaa show you?
There must be communication between the cells in order for only one to form and that no communication is coming from the other cells to these cells and AC is the default state
What genes were found in a screen of Ac/Vu mutants?
Two loss of function genes which caused both cells to convert to Ac (no Vu cell)
What does the phenotype of the Ac/Vu loss of function mutants tell you about the function of the wildtype gene?
It must be involved in the signalling between the two cells
What were the two genes identified by characterising the mutants for ac/vu?
Lin-12 and lag-2
What does lin-12 Wt gene encode?
A transmembrane receptor
What does lag-2 wt gene encode?
A transmembrane receptor ligand
What are lin-12 and lag-2 involved in?
They are involved in juxtacrine signalling betwee nthe z1ppp and the z4aaa which leads to Vu cell fate
Describe the process of juxtacrine signalling between the z1ppp and the z4aaa cells?
They both start off with low levels of lin-12 and lag-2 and randomly one of the cells starts to produce more lin-12 - this little increase is suddenly amplified into lots of lin-12 being produced which also switches off the lag-2 in that cell
How can the lin-12 turn on lag-2 turn off be described as a molecular switch?
Because it goes from being a little random reversible increase to an unstable irreversible increase leading to contant lin-12 in one cell with no lag-2
What is the outcome of one cell producing lots of lin-12 and turning off lag-2?
The other cell produces lots of lag-2 and turns off lin-12
What does the cell that produces lots of lin-12 become?
Vu
What does the cell that produces lots of lag-2 become?
IT stays as the Ac cell and as it is produces the signal to turn the other cell into vu
Why is active lin-12 needed to keep making lin-12?
Because the lin-12 protein is very unstable
What is the lin-12 equivalent in dros. called?
Notch
What is the lin-12 equivalent in humans?
TAN-1
What is the lag-2 equivalent in dros?
Delta
What happens when lag-2(or delta) binds lin-12 (or notch)
It cause proteolytic cleavage of the receptor, the inner bit of which then migrates to the nucleus where it can interact with a CSL protein to activate target proteins
What does a mutation in the notch-1 lead to?
Human T-cell acute lymphoblastic lymphoma
What are the adhesive compotent in cadherins?
desmosomes and adherens junctions
What are desmosomes?
Cell junctions that connect cells via intermediate filaments
What are the adhesive compotents in integrins?
Hemidesmosomes
What are hemidesmosomes?
Connect cells via actin filaments
What are adherens junctions?
Connect cadherins via actin filaments
What are the three groups of adheive molecules between cells?
- Cadhreins
- Immunoglobulin superfamily
- Selectins
What do cadherins interact with?
intermediate filaments and actin filaments
What are integrins?
Adhesions between the cell and the ECM
What is the structure of integrins?
Composed of an alpha and a beta chain
How does the structure of integrins relate to the function?
The alpha subunits binds the ligand and the beta subunit binds actin
How do integrin ligands regulate actin dynamics?
Through Ras (NAPK pathway-nitrogen activated protein kinase)
