Recap 2nd year

Question 1

What molecule is important in the prevention of neural induction and how can this be shown experimentally

Answer 1

BMP2, 4 and 7 found in the animal cap in Xenopus oocytes

mRNA for a truncated BMP receptor into the animal cap leads to the development of neurons instead of epidermis

Question 2

Which molecules in the involuting mesoderm at the blastopore bind to BMP receptors in the neural plate, inhibiting their action (in Xenopus)

Answer 2

Follistatin, Cerberus, Noggin, Chordin - neural induction in this area.

Question 3

What is the invertebrate drosophila gene for BMP2/4

Answer 3

dpp (decapentaplegic)

Question 4

What is the drosophila homologue of chordin

Answer 4

Short gastrulation (sog)

Question 5

On what side of the embryo is the neural plate found

Answer 5

Dorsal

Question 6

What is the molecular pathway for the differentiation of a dorsal ectodermal cell to a neural plate cell.

Answer 6

BMP antagonism induces the activity of smad7, which inhibits smad1.
Smad 7 and low Smad 1 leads to SoxD, Xlpou2 (neuralising TFs) for cells to produce neurogenin, then neuroD which induces neural differentiation

Question 7

Which transcription factor in the organiser induces the expression of chrodin, noggin etc

Answer 7

Goosecoid, Gsc

Question 8

What types of cell movement does axial mesoderm undergo as gastrulation proceeds

Answer 8

Involutes - an epithelial sheet rolls inward to form an underlying layer
Intercalates - rows of cells move between one another, creating an array of cells that is longer (in one or more dimensions) but thinner.
Convergent extension - Rows of cells intercalate, but the intercalation is highly directional.

Question 9

What happens to the organiser after neural plate induction

Answer 9

It begins to differentiate into axial mesoderm - involuting, intercalating and undergoing convergent extension

Question 10

What is invagination

Answer 10

A sheet of cells (epithelial sheet) bends inwards

Question 11

What is ingression

Answer 11

Individual cells leave the epithelial sheet and become freely migrating mesenchyme cells

Question 12

What is an epiboly

Answer 12

A sheet of cells that spreads by thinning

Question 13

What is the importance of the differentiation and movement of the axial mesoderm

Answer 13

Gives rise to the regionalisation of the AP axis

Question 14

What are the domain that make up the forebrain, midbrain and hindbrain

Answer 14

Telencephalon, diencephalon = Forebrain
Mesencephalon = midbrain
Metencephalon + myelencephalon = hindbrain

Question 15

What can be said about the character of the early induced neural plate

Answer 15

Expressing markers that are later confined to the forebrain - Anterior in character

Question 16

What markers are found in the anterior prechordal mesoderm

Answer 16

Cerberus and other BMP/Wnt antagonists,

Question 17

What differs in the notochord and late node compared to the prechordal mesoderm

Answer 17

Provide signals that promote proliferation and growth of neural cells and their posteriorisation

Question 18

What markers are expressed in the notochord/ late organiser

Answer 18

FGF, Wnt, RA

Question 19

What is the role of the specialised border at the edge f the neural plate/ectoderm

Answer 19

Crucial for neural crest formation as well as roof plate formation and dorsal neural tube patterning

Question 20

What is the role of BMPs in relation to neural crest cells

Answer 20

Working with Wnt and FGF signalling - initiate a cascade of events to give rise to a highly potent and proliferative set of neural crest cells

Question 21

What is the role of the notochord in patterning the ventral neural tube

Answer 21

The secreted ligand Shh is expressed in the notochord and then in the floor plate - Acts as a morphogen to induce different progenitor cells along the dorso-ventral axis of the future spinal cord

Question 22

What evidence is there that Shh is a morphogen

Answer 22

Immunohistochemistry shows Shh protein in a gradient, emanating away from its source cells

Question 23

What is the result of Shh morphogen signalling

Answer 23

Different transcription factors appear in bands of progenitor cells along the d-v axis.

Question 24

What happens to progenitor cells along the d-v axis as they differentiate q

Answer 24

They move laterally