Axis Specification and Gastrulation in C. Elegans

Question 1

C Elegans: Phase 1

Answer 1

P0 [posterior] cell only.

Question 2

C Elegans: Phase 2

Answer 2

P0 splits into AB and P1

Question 3

C Elegans: Phase 3

Answer 3

AB splits into ABa and ABp. P1 splits into the P2 and EMS

Question 4

What does EMS stand for?

Answer 4

Endoderm, Mesoderm

Question 5

C Elegans: Phase 4

Answer 5

The most important things, is that the EMS splits into the MS and the E, whereas the P2 splits into the C and P3.

Question 6

What component marks the anterior of the worm cell?

Answer 6

Polar body

Question 7

Step 1: Which side does the sperm usually enter from?

Answer 7

The anterior of the cell

Question 8

Where do the P granules localize to once the sperm enters?

Answer 8

the posterior

Question 9

Step 2: Protein assymtetries–>Group the association of PAR-3&6, PAR-2, MEX-5

Answer 9

PAR-3&6 are part of the anterior cortex, PAR-2 part of the posterior cortex, MEX-5 localizes to the anterior

Question 10

What causes movement of the cortical domain?

Answer 10

Actin and myosin movement

Question 11

Step 3: More protein rearrangement

Answer 11

PIE-1 AND SKN-1 only show up in the P1 posterior cell, because MEX-5, which is only in the anterior AB cell degrades any PIE-1 and SKN-1 there.

Question 12

What does MEX-5 do in regards to PIE-1 and SKN-1

Answer 12

MEX-5 degrades PIE-1 and SKN-1 due to ubiquitin pathways

Question 13

Step 4: PIE 1 …

Answer 13

represses SKN-1 activity in P2, but does not destroy it

Question 14

Step 4: So where does SKN-1 act?

Answer 14

SKN-1 is in the EMS and P2, but it only acts in EMS, because PIE-1 counteracts SKN-1, and PIE-1 is only degraded by MEX-5 which is not in P2.

Question 15

What does lack of SKN1 create?

Answer 15

It causes “skin in excess”, which shows up as lack of the pharynx.

Question 16

Step 5: In the EMS, what does the presence of SKN-1 create?

Answer 16

It allows the activation of MED proteins that activate transcription of mesodermal and endodermal genes in the MS & E.

Question 17

Step 6: What is mom-2, and what is mom-5?

Answer 17

Mom 2 is the Wnt, and Mom 5 is the frizzled receptor.

Question 18

Step 6: How is Wnt signaling used?

Answer 18

P2 sends the Wnt MOM-2 to the neighboring EMS cell causing the close on to turn into endoderm.

Question 19

What does MOM stand for?

Answer 19

More mesoderm

Question 20

Which two cells undergo ingression?

Answer 20

Ea and Ep

Question 21

For Ea and Ep to perform ingression, which two cells cover up the space?

Answer 21

P4 and MS

Question 22

What is it called when the epidermis undergoes epiboly to cover interior cells?

Answer 22

Ventral enclosure.