L14: Xenopus Gastrulation

Question 1

What is the outcome of gastrulation?

Answer 1

Three primordial layers: ectoderm, mesoderm, endoderm

Question 2

What are 5 types of cellular movements in gastrulation?

Answer 2

1. Invagination
2. Ingression
3. Involution
4. Delamination
5. Epiboly

Question 3

Invagination

Answer 3

clefting in

Question 4

Ingression

Answer 4

individual EMT

Question 5

involution

Answer 5

single layer wrapping inside

Question 6

delamination

Answer 6

group EMT in one layer

Question 7

Epiboly

Answer 7

3D involution

Question 8

Why study frog?

Answer 8

• Fast growth
• Well documented
• Microsurgery
• large and abundant embryo

Question 9

In how many hours after fertilization does gastrulation happen in xenopus?

Answer 9

10 hours

Question 10

How many cells in gastrula?

Answer 10

30,000

Question 11

What is morpholine?

Answer 11

A structure similar to de/oxyribose sugar in DNA and RNA that it replaces

Question 12

Function of morpholino oligo

Answer 12

It makes translational complex unable to form by binding to start codon. since it says in the system for a long time, it enables long term, specific mis-expression of genes than siRNA

Question 13

Why is the blastocoel gap important?

Answer 13

• it prevents interactions between the roof and floor

- Provides space for cell migration in gastrulation

Question 14

How is blastocoel roof help together?

Answer 14

cell-cell adhesion: tight and gap junctions

Question 15

What happens to blastocoel roof if EP-cadherin is negated?

Answer 15

BTR falls apart

Question 16

What are the sides in blastula?

Answer 16

Animal and vegetal

Question 17

Where is the dorsal lip of the blastopore?

Answer 17

in the vegetal side

Question 18

Draw the transition due to epiboly in gastrulation in midsagital cut. (Label the blastopore lip, gut, mesoderm, ectoderm, endoderm)

Question 19

How does fibronectin form fibril?

Answer 19

• Comes in dimer form.
• Binds to cell surface with Integrin a5ß1
• Expands around the cell membrane
• Forms fibril through self-polymerization

Question 20

What physical changes take place in ectoderm before gastrulation?

Answer 20

• Superficial layer extends

- Radial intercalation in deep layer

Question 21

What is required for intercalation?

Answer 21

• A5ß1integrin
• Fibronectic network
• C3 and C3r

Question 22

Without FN, what does not happen properly?

Answer 22

cell polarity, shown by the location of mitotic fibrils

Question 23

What are the two functions of C3?

Answer 23

• intercalation

- cell protrusion towards superficial cells

Question 24

What is the mechanism of protrusion due to c3?

Answer 24

unknown

Question 25

What is the PDGF pathway?

Answer 25

• PDGF > PI3K
  
  • > Cdb42 > filopodia
  • > Rac1 > lamellipodia
  • > Rho > actin, stress fibres, adhesions

Question 26

What must be located between the mesoendoderm and ectoderm for there to be directional movement towards animal side?

Answer 26

FN with PDGF gradient

Question 27

Removing which stuff means no movement? (5 things)

Answer 27

• FN
• PDGF
• PDGFR
• PI3-K

Question 28

What are two types of PDGF

Answer 28

truncated and long form

Question 29

Which PDGF is required and why?

Answer 29

long form because truncated doesnt bind to FN. Both bind to PDGFR

Question 30

What do bottle cells do?

Answer 30

Push the meseoenderm towards the outer edge. keeping the curvature

Question 31

Why does the cell perform epiboly?

Answer 31

to create the mesoderm.

Question 32

What is the importance of interacalation?

Answer 32

pushes the cells to become mesoderm through epiboly.