Communication Between Cells

Question 1

What is the body plan of C.elegans?

Answer 1

Ectoderm (skin aroud the outside) followed by mesoderm (body wall, muscle) then endoderm (gut) in the middle

Question 2

Where are the gonads found in c.elegans?

Answer 2

In the space between the body wall and the intestine

Question 3

How are the neurons of c.elegans positions?

Answer 3

In a nerve ring

Question 4

What is useful about the c.elegans embryo?

Answer 4

It is transparent throught embryogenesis so can follow and map cell divisions

Question 5

How many somatic nuclei are in the adult hermaphrodite?

Answer 5

959

Question 6

How many somatic nuclei does the adult male have?

Answer 6

1031

Question 7

Why is mapping very accurate in c.elegans?

Answer 7

Because is it a largely invariant process

Question 8

What kind of signalling is involved in that of the c.elegans gonad?

Answer 8

Juxtacrine

Question 9

What are the four cells of the L1 gonad?

Answer 9

Z1-4

Question 10

What do Z2 and Z3 make?

Answer 10

The germline

Question 11

What do Z1 and Z4 make?

Answer 11

The somatic tissue of the gonad

Question 12

What cells are present in the L2 gonad?

Answer 12

The Z2 and Z3 for the germline and 12 somatic cells including z1ppp and z4aaa

Question 13

What do z1ppp and z4aaa differentiate into?

Answer 13

Anchor and ventral uterine cells (either has the ability to make each kind but only one of each kind is made)

Question 14

What happens if you leave only z1ppp or z4aaa and kill all other cells?

Answer 14

Ac always forms

Question 15

What happens if you kill only z1ppp or z4aaa and leave all other cells?

Answer 15

Ac always forms

Question 16

What happens if you leave z1ppp and z4aaa and kill all other cells?

Answer 16

Ac and Vu are formed

Question 17

What does the experiment of z1ppp and z4aaa show you?

Answer 17

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

Question 18

What genes were found in a screen of Ac/Vu mutants?

Answer 18

Two loss of function genes which caused both cells to convert to Ac (no Vu cell)

Question 19

What does the phenotype of the Ac/Vu loss of function mutants tell you about the function of the wildtype gene?

Answer 19

It must be involved in the signalling between the two cells

Question 20

What were the two genes identified by characterising the mutants for ac/vu?

Answer 20

Lin-12 and lag-2

Question 21

What does lin-12 Wt gene encode?

Answer 21

A transmembrane receptor

Question 22

What does lag-2 wt gene encode?

Answer 22

A transmembrane receptor ligand

Question 23

What are lin-12 and lag-2 involved in?

Answer 23

They are involved in juxtacrine signalling betwee nthe z1ppp and the z4aaa which leads to Vu cell fate

Question 24

Describe the process of juxtacrine signalling between the z1ppp and the z4aaa cells?

Answer 24

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

Question 25

How can the lin-12 turn on lag-2 turn off be described as a molecular switch?

Answer 25

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

Question 26

What is the outcome of one cell producing lots of lin-12 and turning off lag-2?

Answer 26

The other cell produces lots of lag-2 and turns off lin-12

Question 27

What does the cell that produces lots of lin-12 become?

Answer 27

Vu

Question 28

What does the cell that produces lots of lag-2 become?

Answer 28

IT stays as the Ac cell and as it is produces the signal to turn the other cell into vu

Question 29

Why is active lin-12 needed to keep making lin-12?

Answer 29

Because the lin-12 protein is very unstable

Question 30

What is the lin-12 equivalent in dros. called?

Answer 30

Notch

Question 31

What is the lin-12 equivalent in humans?

Answer 31

TAN-1

Question 32

What is the lag-2 equivalent in dros?

Answer 32

Delta

Question 33

What happens when lag-2(or delta) binds lin-12 (or notch)

Answer 33

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

Question 34

What does a mutation in the notch-1 lead to?

Answer 34

Human T-cell acute lymphoblastic lymphoma

Question 35

What are the adhesive compotent in cadherins?

Answer 35

desmosomes and adherens junctions

Question 36

What are desmosomes?

Answer 36

Cell junctions that connect cells via intermediate filaments

Question 37

What are the adhesive compotents in integrins?

Answer 37

Hemidesmosomes

Question 38

What are hemidesmosomes?

Answer 38

Connect cells via actin filaments

Question 39

What are adherens junctions?

Answer 39

Connect cadherins via actin filaments

Question 40

What are the three groups of adheive molecules between cells?

Answer 40

1. Cadhreins
2. Immunoglobulin superfamily
3. Selectins

Question 41

What do cadherins interact with?

Answer 41

intermediate filaments and actin filaments

Question 42

What are integrins?

Answer 42

Adhesions between the cell and the ECM

Question 43

What is the structure of integrins?

Answer 43

Composed of an alpha and a beta chain

Question 44

How does the structure of integrins relate to the function?

Answer 44

The alpha subunits binds the ligand and the beta subunit binds actin

Question 45

How do integrin ligands regulate actin dynamics?

Answer 45

Through Ras (NAPK pathway-nitrogen activated protein kinase)