L8 - Neurogenesis

Question 1

What happens to cells that remain at the ventricular zone?

Answer 1

They exist as radial glia - neural stem cells
Cell body sits in ventricular zone but process extends to outer surface
Pool of undifferentiated cells used to build up the nervous system

Question 2

Early neural tube

Answer 2

Is one cell wide – neuroepithelium

Question 3

Interkinetic migration

Answer 3

In the early neural tube the cells are proliferating and their nuclei undergo interkinetic migration

• G1 and S phase - nucleus is away from the lumen
• M phase and cytokinesis - nucleus is close to the lumen
• Cytokinesis - lateral attachment is lost then reforms

Question 4

Early neuroepithelial cell division

Answer 4

It is symmetrical
Two identical daughters
- Start to change shape and become radial glial like

Question 5

Radial glia division

Answer 5

It is asymmetrical

• 1 radial glia
• 1 will differentiate into a neurone

Question 6

What is the scaffold used by radial glia daughter cells?

Answer 6

Neuron daughter cell uses the scaffold provided by its sister to migrate away from the ventricular zone

Question 7

What determines whether 2 radial glial daughters vs 1 radial glia and 1 neurone

Answer 7

Cell division plate

Question 8

In a cell with cytoplasmic or membrane determinant that is asymmetrically localised- division vertically

Answer 8

2 identical daughter cells

- Both identical to mother

Question 9

In a cell with cytoplasmic or membrane determinant that is asymmetrically localised- division along equator

Answer 9

2 different daughter cells

- Radial glial progenitor and a cell that has different determinants

Question 10

Role of notch in wildtype Drosophila

Answer 10

A few cells become neurones

Question 11

Role of notch in proneural mutant Drosophila

Answer 11

No achaete scute

No cells become neurones

Question 12

Role of notch in neurogenic mutant Drosophila

Answer 12

No notch

More cells become neurones

Question 13

Conclusion of role in notch in formation of neurones

Answer 13

If cell does not see Notch then more neurones form

Question 14

What is lateral inhibition?

Answer 14

Used to make initially similar cells different from one another

Question 15

Lateral inhibition method

Answer 15

1. Transmission of inhibitory signal between a pair/cluster of cells to prevent cells from adopting a particular fate
2. Initially both cells equally capable of making and receiving inhibitory signal
3. A change is introduced so that one cell makes more inhibitory signal
4. Second cell receives more inhibitory signal becoming inhibited
5. To stabilise this change, inhibited cell must be prevented from continuing to send inhibitory signal

Question 16

Notch regulating lateral inhibition in neurogenic tissue

Answer 16

1. Both cells are making same amount of achaete scute, delta and notch
2. Slight imbalance in notch signalling causing increased delta in cell 1
3. Notch signalling pathway activated in cell 2
4. Chain of transcriptional event that repress the transcription of achaete scute so delta no longer maintain in cell 2
5. Cell 1 no longer receives notch so no repression of achaete scute
6. Ascute expressed at high level and cell 1 becomes a neuron

Question 17

Role of delta in lateral inhibition

Answer 17

Inhibitory signal

Question 18

Role of notch in lateral inhibition

Answer 18

Receptor

Represses achaete scute

Question 19

Role of achaete scute proteins in lateral inhibition

Answer 19

Maintain delta

Question 20

What bilateral fate decisions is notch involved in?

Answer 20

A single cell divides into 2 and have to decide on fate:
Stay as dividing stem cell or differentiate?
Glial progenitor or neural precursor?
Neuron or oligodendrocyte?
Roof plate or neural crest cell?