Ventralisation

Question 1

What do the most ventral progenitor cells in the neural tube differentiate into?

Answer 1

Motor neurons

Question 2

How is the ventral neural tube patterned?

Answer 2

1. Shh secreted by notochord and then the floor plate
2. Shh forms a morphogen gradient from ventral to dorsal
3. Different concentrations of Shh signalling induces expression of different transcription factors in progenitor blocks along DV axis
4. progenitor cells proliferate to form 1 identical daughter cell remaining in ventricular zone and another daughter cell that migrates laterally and becomes a neuron
   - results in layers of neural tube built up at mantle zone
5. neuron extends an axon

Question 3

Ptch

Answer 3

Receptor with 12 transmembrane domains

Question 4

Smo

Answer 4

Receptor with 7 transmembrane domains

Question 5

Holoprosencephaly

Answer 5

Failure of the ventral forebrain to form due to Shh-/- signalling. Cyclopia, abnrmal limbs/digits and lack of pituitary is observed.