A-P regionalisation and Dorsalisation

Question 1

What identities do BMP antagonists induce? And where are they expressed

Answer 1

BMP antagonists induce a neural identity of anterior character.
They come from the early Node/organiser, and are maintained in the prechordal tissue

Question 2

Which cells express Wnt,FGF etc and what do they do?

Answer 2

Cells from the later Node/Organiser

These signals promote growth and posteriorisation

Question 3

What are HOX genes?

Answer 3

Family of genes that control segmental identity in insects

There are many different hox genes- each expressed in a specific region along the A-P axis

Question 4

What activates a HOX gene?

Answer 4

Particular (threshold) concentrations of posteriorising signals- for example- retinoic acid (RA)
RA gradient induces different patterns of hox transcription

Question 5

Where are the HOX genes Hoxa1 and Hoxb1 expressed?

Answer 5

In the rhombomeres 4 and 5 respectively.

The abducens nerve forms in this region

Question 6

What cells do the neural plate border cells give rise to?

Answer 6

Neural crest cells

Roof plate cells

Question 7

What determines what the NCC will differentiate into?

Answer 7

1. Position of origin of the NCC
2. Time of generation of the NCC
3. The migratory pathway and signals the NCC encountered

Question 8

What are the roof plate cells important for?

Answer 8

1. Neurulation

2. Dorsal neural tube patterning

Question 9

What do the roof plate cells upregulate, and what is the effect of this

Answer 9

They upregulate BMPs and Wnts

They induce expression of T factors that cause neural tube progenitors to acquire dorsal identities