Lecture 5

Question 1

Border of Neural Plate

Answer 1

Specialised cell forms known as neural plate border cell
- induced by a medium concentration of BMP
- separates neural plate & epidermal cells in the ectoderm

Question 2

Specialisation pathway for Neural Plate Border Cells

Answer 2

ectoderm –> Border cells –> Neural crest cell –> PNS

Question 3

Importance of Border Cells

Answer 3

1) Neural Crest Formation
2) Roof Plate formation
3) closure of neural tube (terminating step of neurulation)

Question 4

Final Location of NP Border cells

Answer 4

Come to sit at the top of the neural tube

Question 5

Neural Crest Formation: Step 1)

Answer 5

Initial border arises due to expression of Msx transcription factor.
- induced by the intermediate levels of BMP signalling

Question 6

NCF Step 2)

Answer 6

at the border, a transcriptional signature rapidly develops - that develops the progenitors for the neural plate border cells.

Question 7

NCF step 3)

Answer 7

Other Transcription factors are upregulated in the NPBC’s
- provide ‘stem-cell like’ properties: multipotency & proliferation
- e.g. c-Myc, Id, Snail, Sox
- These TFs activate genes for survival, multipotency & proliferation
– These TFs drive NPBCs to ‘neural crest’ identity.

Question 8

NCF step 4)

Answer 8

Another set of neural plate TFs upregulate genes promoting EMT
- Epithelial-mesenchymal transition
- properties change from epithelial to mesenchymal (stem-like).

Neural crest cells delaminate (separate) from the border cells and begin to migrate away.

Question 9

Summary of Neural Crest Formation

Answer 9

No need to remember names for TFs
- appreciate: a network of TFs in neural plate border cells is established over time
- contorlling cell behaviour: including proliferation, multipotency, survival + delamination & .migration

Question 10

End of Neurulation

Answer 10

Once the neural crest cells have migrated out the neural tube is finally closed.

Question 11

Neural Crest cells

Answer 11

known as 4th ‘germ layer’
- can give rise to a wide range of cells in the body.

The fate of crest cells is determined by:
1) Position of origin –> influenced by HOX genes
2) TIME of generation
3) the Migratory Pathway they take and any signals they encounter on their way.

Question 12

Crest cell fates

Answer 12

Migrate dorsally down from the neural tube.
The different pathways determine fate:
- sensory ganglia/neurons
- can migrate towards somite’s -> towards the aorta –> forming sympathetic and parasympathetic ganglia

Question 13

Roof Plate Cells

Answer 13

Some neural plate border cells remain at the border forming Roof Plate Cells.
- important for tube closure and for patterning this top/dorsal region.

Question 14

Roof plate cells & BMP

Answer 14

Upregulate BMPs.
BMPs secreted (locally) into the unpatterned neural tube.
Induces expression of transcription factors - which encode Pax genes
- Pax genes act intrinsically –> inducing dorsal identity in the neural tube

• Pax genes also upregulate BMPs –> creates a relay of BMP signalling in the dorsal neural tube.

Question 15

Roof Plate BMP mechanism of action

Answer 15

Originally thought a singular BMP acted as a morphogen to induce dorsal identity. X

Instead

Different BMPs are present –> inducing different cell types.
- the different progenitors will differentiate into distinct neuronal subsets (next lecture).