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Question 1

what is the neural plate?

Answer 1

single cell thick neuroepithelium which is induced by ectoderm on dorsal side of embryo (BMP antagonists)

Question 2

where does the neural plate sit?

Answer 2

sits above mesoderm and endoderm
- grows and elongates along AP axis then roles into neural tube (neuralation)
(above prechordal mesoderm/notochord)

Question 3

how do neural plate cells form?

Answer 3

via DIFFERENTIATION

- cells become different to one another and aquire specialised properties which are caused by changes in gene expression

Question 4

what is gene expression governed by?

Answer 4

both extrinsic factors (morphogens) and instrinsic factors (TFs)

Question 5

give the two fates of an ectoderm determined by BMP

Answer 5

• BMP antagonism - neural plate cell

- BMP agonism - epidermal cell

Question 6

What TFs does the spemann organiser release?

Answer 6

• BMP ANTAGONISTS
• noggin
• chordin
• gsc
• follastatin

Question 7

where is the neural plate induced?

Answer 7

-induced in dorsal ectoderm where BMP is inibited

by BMP antagonists released by organiser

Question 8

what TFs are released ventrally?

Answer 8

BMP4

tolloid

Question 9

what happens to spemann organiser once it begins to induce the neural plate?

Answer 9

It differentiates into axial mesoderm

notochord, prechordal mesoderm, anterior endoderm

Question 10

what happens to AM when spemann organiser is differentiated?

Answer 10

axial mesoderm involutes, intercalates and undergoes convergent extension - extends anteriorly.
-released BMP antagonists

(led by leading edge cells)

Question 11

what happens in convergent extension?

Answer 11

sheet of cells changes shape by extending in one direction and narrowing and converging in another. (cells intercalate)

Question 12

where are BMP antagonists maintained in axial mesoderm?

Answer 12

• BMP antagonists are only maintained in the prechordal mesoderm.
• node changes and node and notochord stop producing BMP antagonists (promote proliferation and posteriorisation)

Question 13

what are the characteristics of the late node and notochord?

Answer 13

• change BMP antagonistic properties

- - have new characteristics which promote proliferation and growth of neural cells and POSTERIORISATION

Question 14

what are posteriorising signals?

Answer 14

• Fgf, Wnt and RA

- promote growth and posteriorisation

Question 15

where are BMP and Wnt antagonists maintained?

Answer 15

maintained anteriorly in prechordal mesoderm

Question 16

what do the specialised border of cells at the edge of the neural plate and ectoderm express?

Answer 16

msx

Question 17

what leads to dorsalisation?

Answer 17

Bmps work with Wnts and FGF signalling toinitiate cascade of events which lead to dorsalisation
-gives rise to NCCs

Question 18

what are edge cells crucial for?

Answer 18

• neural crest cell formation
• patterning of the dorsal NT
• roof plate formation

Question 19

how does neural tube ventralisation occur?

Answer 19

• there is secreted Shh in notochord and then floorplate
• Shh acts as a morphogen to induce different progenitor cells along D-V axis of future spinal cord
• Shh diffused from NT and FP to induce a conc gradient - cells have different thresholds - different responses to Shh gradient
• different TFs are induced in bands of of different progenitors along DV axis - read out of Shh gradient

Question 20

where do differentiating cells move?

Answer 20

move laterally

Question 21

Give the pathway from the ectoderm when BMP antagonists are present

Answer 21

• ectoderm exposed to BMP antagonists
• low Smad1, high smad 7
• neuralating TFs activated
• neurogenin
• neuroD
• neural differentiation

Question 22

Give the pathway from the ectoderm when BMP is present

Answer 22

ectoderm - exposed to BMPs

• hgh smad1, low smad 7
• epidermalizing TFs
• LEF1
• epidermal differentiation