Gastrulation

Question 1

What does the ICM segregate into in humans ?

Answer 1

Epiblast - give rise to 3 germ layers

Hypoblast - yolk sac and extrembryonic mesoderm

Question 2

What are the five stages of gastrulation?

Answer 2

Invagination 
Involution 
Delamination
Ingression 
Epiboly

Question 3

What is ingression ?

Answer 3

formation of primary mesenchymal cells (PMCs)
lose cadherins ( E, alpha, beta)
lose affinity for neighbouring cells
gain affinity for basal lamina

Question 4

What do eomes do?

Answer 4

TF
specifies mesoderm
represses Wnt signal for dorsalisation

Question 5

What does the organiser do?

Answer 5

initiates gastrulation and patterns embryo

results in formation of neural tube by dorsalizing ectoderm

Question 6

What forms the Nieuwkoop centre ?

Answer 6

Vg1, VegT and beta-catenin

Question 7

What does the nieuwkoop centre do?

Answer 7

produces mesodermal - inducing and dorsalising signals which form the organiser

Question 8

What is the mechanisms of organiser formation?

Answer 8

mesoderm induction by vegetal endoderm

Dorsal endoderm cells in vegetal pole express Vg1, VegT and beta-catenin

Question 9

What paracrine factors are secreted by the organiser to specific the neural plate ?

Answer 9

Noggin
Chordin
Cerberus