Neuronal migration - somal and terminal translocation

Question 1

What does the marginal zone contain?

Answer 1

Radial glial cells and Cajal-Retzius cells and migrating interneurons

Question 2

What does dual-signalling from Cajal-Retzius cells do?

Answer 2

Secretes protein reelin and cell adhesion proteins: nectins

Question 3

What are reeler mice and what is wrong with them?

Answer 3

Have a spontaneous mutant reeler phenotype. Causes their cortex to lose its layers and become slightly inverted. All other lamina structures of the brain are affected.

Question 4

What receptors does reelin bind to and what molecule is recruited after its bound?

Answer 4

Binds to receptors VLDR and APO3R2 on cell surface. This recruits Dab1 which is phosphorylated at the membrane.

Question 5

What does Dab1 do?

Answer 5

Signals through different signalling pathways which leads to Rap1/ GSK3Beta or N-lofilin

Question 6

What happens if you stop the secretion of Dab1?

Answer 6

You completely eliminate reelin signalling

Question 7

What phenotype does the spontaneous mutant for Dab1 show?

Answer 7

Same phenotype as reeler mice

Question 8

What method can be done to eliminate reelin signalling?

Answer 8

Using Dab1 flox/flox mouse

Question 9

How can you use Dab1 flox mice to eliminate the Dab1 gene?

Answer 9

Electroporation of Cre with a neuronal specific promoter - therefore only neurons will recombine away the Dab1 gene

Question 10

How do we know that reelin is important for somal and terminal translocation?

Answer 10

If you do the Dab1 flox mice method in later stages of neuronal development - will see that the neurons are initially able to move but will always stay below the region they are meant to be in, in the absence of reelin

Question 11

What are the different ways you can manipulate/ mess up the different pathways of Dab1 in order to observe what they do?

Answer 11

1. If kinase is involved - put a mutated/ non-phosphorylated kinase in
2. If you need view effect of phosphorylation - mutate the AA that would have been phosphorylated and it wont be phosphorylated anymore
3. If you want to see how the lack of GTPase will affect anything - over express a protein that will inactivate it

Question 12

How was the migration of cells affected when interfering with Limk1, Cofilin or Akt1?

Answer 12

No difference - the cells were able to move up to the cortical plate

Question 13

What happened to the cells when Rap signalling was being interfered with?

Answer 13

Cells had problems migrating therefore Rap1 is needed for somal translocation

Question 14

What is Rap1?

Answer 14

A GTPase that regulates cell adhesion through adhesins and integrins

Question 15

What does interfering with cadherins at early stages do to migration?

Answer 15

Blocks migration

Question 16

What happens if you interfere with Rap1 in early stages?

Answer 16

Get less cadherin on the cell surface

Question 17

How can you counteract the affects of Rap1 interference on cadherin?

Answer 17

Put excess cadherin in and you can counteract this and restore migration. Therefore more cadherin goes to the surface and will be used to attach to the marginal zone and pull the cells up

Question 18

What do Cajal-retzius cells secrete to trigger its pathway?

Answer 18

Secretes reelin

Question 19

What molecule is on the surface of cajal-retzius cells and what does it interact with?

Answer 19

Nectin1 which will interact with nectin3 which is on the surface of migrating neurons.

Question 20

Where is a prime site for cadherin adhesion to take place?

Answer 20

Places where the addition of nectins to the system as well as other systems

Question 21

What does the reelin signalling pathway facilitate the recruitment of?

Answer 21

CDH2 to sites of nectin1 and 3 additions which initially provide weak additions but then get stabilised by CDH2

Question 22

What is stabilisation of nectin1 and 3 addition sites dependent on?

Answer 22

• The function of afadin as an intracellular partner of nectins, and P120 as an intracellular partner of CDH2, and Rap1 which allows afadin to bind to p120.
• Thus allowing neurons to complete migration through somal translocation