NEURAL CREST AND FORMATION OF THE PNS

Question 1

At the same time as building an anterior - posterior axis, a dorsal- ventral axis is also being set up. At the same time as this, cells are being induced that will gives rise to the entirety of the PNS. What cells are these?

Answer 1

The neural crest cells.

Question 2

During neural induction, cells that receive high levels of BMP antagonists such as chordin will be induced to become neural (due to induction of Sox). However, BMP antagonists have a diffusion gradient. What happens to cell that receive ‘some’ BMP antagonists?

Answer 2

A specialised border forms at the neural - ectoderm boundary called the neural plate border. Within this border, cells are called neural plate border cells.
As the neural plate folds up, these cells will form the most dorsal aspect of the neural tube.

Question 3

Neural crest formation and dorsal neural tube patterning both occur before what is expressed in the notochord?

Answer 3

Shh

Question 4

As neurulation finishes ie. the neural tube is fully closed, the neural crest border cells now form the most dorsal aspect of the neural tube, also knows as what?

Answer 4

The roof plate

Question 5

An early border between the neural plate and surface ectoderm. This occurs where there are intermediate levels of BMP antagonism. This causes an upregulation in what transcription factors to induce neural plate border cells?

Answer 5

Msx which, in combination with other signals, act to turn on other transcription factors such as Pax3, Zic1 and Pax7.
These transcription factors characterise the neural plate border cell.

Question 6

What are the transcription factors that characterise the neural plate border cells?

Answer 6

Msx, Pax3, Pax7, Zic1 to name a few.

Question 7

The transcription factors that characterise neural plate border cells act together with Wnt to upregulate further transcription factors that characterise neural crest cells. What are these transcription factors?

Answer 7

C-Myc, Id and Snail to name a few.

Question 8

What type of cell do transcription factors such as c-Myc, Id and Snail characterise?

Answer 8

Neural crest cells.

Question 9

What is the role of transcription factors such as c-Myc, Id and Snail?

Answer 9

To give stem cell like behaviours such as proliferation (c-Myc), multipotency (Id) and epithelial to mesenchymal transition (Snail).

Question 10

The cells expressing high levels of Snail will leave the neural crest and migrate. The cells that stay become what kind of cells?

Answer 10

Roof plate cells.

Question 11

What marks the end of neurulation?

Answer 11

After the neural crest cells have migrated out the neural tube closes.

Question 12

Some neural crest cells migrate into the somites. What does this give rise to?

Answer 12

The sensory nervous system.

Question 13

Neural crest cell types are determined by what factors?

Answer 13

1. Position of origin
2. Time of generation
3. Migratory pathway

Question 14

What do neural crest cells have the potential to become?

Answer 14

PNS, adrenal medulla, melanocytes, facial cartilage, dentine of teeth

A large variety of cell types

Question 15

Not all neural plate border cells form neural crest cell. A few are retained at the border and form what?

Answer 15

Roof plate cells

Question 16

What are roof plate cells important for?

Answer 16

The final step of neurulation

Dorsal neural tube patterning

Question 17

Roof plate cells themselves begin to upregulate what transcription factors?

Answer 17

BMPs and Wnts

Question 18

What is the role of BMPs and Wnts being secreted from the roof plate?

Answer 18

They diffuse into the dorsal neural tube inducing expression of transcription factors such as Pax6, Pax7, Pax3, Lim1 that cause neural tube progenitors to acquire dorsal identities.

Question 19

What is thought about the BMPs coming from the roofplate.

Answer 19

It was thought that BMPs act as morphogens to induce different cell types but recent work suggests it is many different BMPs inducing many different cell types.