Ventralisation

Question 1

What lies just below the ventral midline?

Answer 1

The floor plate

The notochord

Question 2

What experimental evidence is there to confirm that ventralisation is mediated by the notochord/floor plate?

Answer 2

Graft a piece of donor notochord to an ectopic position on a host embryo
Ectopic floor plate and ventral neurons are induced

Question 3

What does Shh induce and how

Answer 3

Induces ventral identities (ventral neurons)
Shh diffuses through the spinal cord, producing a gradient (high in ventral region, low in dorsal region)
Shh induces expression of T factors in progenitor cells, these T factors confer ventral neural tube identities

Question 4

What experimental evidence is there to confirm that Shh induces ventral identities?

Answer 4

Ectopic floor plate and ventral neurons are induced after implantation of Shh soaked bead

Question 5

What is holonprosencephaly?

Answer 5

Failure of the ventral forebrain to form

Caused by mutations in Shh signalling