c.elegans asymmetric division

Question 1

What two cells does P0 divide into in the 1st cell division of zygote development?

Answer 1

AB and P1 cells

Question 2

What cell lineages do the two daughters of first ACD have?

Answer 2

AB goes on to be somatic cells, such as hypodermis and neural cells
P1 has a somatic lineage (EMS) for gut and muscles cells, and also has germline lineage

Question 3

What two maternal transcripts are cell fate determinants in ACD?

Answer 3

PIE-1 and MEX-5

Question 4

What role does sperm play in ACD of oocyte?

Answer 4

Point of sperm entry determines posterior pole of zygote development

Question 5

what is the phenotype of pie1- mutant?

Answer 5

Germline lineage lost and EMS upregulated

Question 6

What is the basic mechanism that drives ACD in C.elegans?

Answer 6

Intrinsic polarisation

Question 7

What role does MEX-5 in polarisation of zygote?

Answer 7

MEX-5 inhibits PIE-1

Question 8

How do MEX-5 and PIE-1 in the cell?

Answer 8

MEX-5 binds ZIF-1 an E3 Ub ligase causing it to bind PIE-1 and targeting it for degradation

Question 9

How does PIE-1 initiate a germline cell lineage?

Answer 9

Inhibits transcriptional elongation on differential genes by phosphorylation

Question 10

What happens in the cell if AB cell is specifically lysed in laboratory conditions?

Answer 10

P1 still divides and is as would be expected in WT

Question 11

What does the result of lysing AB cell tell you about the mechanism of ACD in zygote?

Answer 11

no compensation for AB lineage confirms that ACD is preceeded by intrinsic polarization of MEX-5/PIE-1

Question 12

What did maternal screens for polarization defects discover?

Answer 12

PAR proteins involved in the polarisation of MEx-5 and PIE-1

Question 13

Which PAR proteins are localised at which poles?

Answer 13

PAR1 and PAR2 are found at the posterior

PAR3 and PAR4 are found at the anterior

Question 14

How are the PAR proteins have exclusivity of domains?

Answer 14

PAR 3 and PAR 6 inhibit PAr1 and PAR2 (inhibit eachother back)
In an unfertilised egg, PKC3 excludes PAR1 and PAR2 from the cortex
Cytoplasmic flow caused by cortical ruffling allows PAR1 and PAR2 to locate to the posterior, as flow pushes PAR3, PAR6 and PKC3 to the anterior clearing posterior region for PAR1 and PAR2

Question 15

What causes cortical ruffling?

Answer 15

Sperm entry relaxes actin filaments at the posterior pole

Question 16

How was the importance of actin in ACD discovered?

Answer 16

Treated developing cells with cytochalasin D, which disrupts actin microfilaments.
This messes up the developmental polarity and sperm entry point no longer is relevant

Question 17

How does PAR protein localisation influence polarization of cell fate determinants?

Answer 17

PAR1 at the posterior pole can phosphorylate MEX-5, blocking its RNA/protein binding function. This means it cannot inhibit PIE-1.
This phosphorylation can be reversed by phosphatase at the anterior pole

Question 18

What structure does sperm contain that may contribute to actin events following sperm entry?

Answer 18

centrosome - actin containing organelle