cell polarity

Question 1

why is cell polarity important for the function of the cell

Answer 1

regions of the cell will require different proteins for different functions

Question 2

why is budding yeast a good example for cell polarity (3)

Answer 2

unicellular
the genome is known and annotated
obvious internal and external signals of polarity

Question 3

how do haploid and diploid cells bud, in terms of location off the cell surface

Answer 3

haploid= axial pattern- directly adjacent to eac
Diploid= bipolar pattern- at either side of the poles

Question 4

3 genes involved in both axial and bipolar budding

Answer 4

BUD1, BUD2, BUD5

Question 5

the budding genes involved in both axial and bipolar budding, what are their function

Answer 5

they decode the axial and bipolar marks and SIGNAL the machinery involved in generating the polarity axis

Question 6

what does a mutation in the BUD1, BUD2 and BUD5 genes result in

Answer 6

random budding pattern in both haploid and diploid cells

Question 7

what cycle do the BUD1/2/5 genes function in

Answer 7

GTPase cycle

Question 8

what proteins are very important for polarity establishment (family and certain protein)

Answer 8

1. Rho-GTPases
2. Cdc42

Question 9

what type of sensitivity mutant is Cdc42

Answer 9

temperature sensitive
24 degrees= polarisation= bud, grow and divide
37 degrees= isotropic growth- no axis of polarity

Question 10

how does Cdc24 activate Cdc42 as the GEF in a GTPase cycle

Answer 10

Cdc24 will bind to an activated gene, the BUD1 gene. This allows the activation of Cdc42

Question 11

The activation of Cdc42 results in?

Answer 11

polarity site to become established

Question 12

what are the Cdc42, 24 and 43 proteins part of and involved in

Answer 12

polarity site to be established
Rho-GTPases

Question 13

the Ste2 and Ste3 receptors bind to alpha-factor and a-factor repectively, what cells secrete these pheromones

Answer 13

MATa
MAT(alpha)

Question 14

what type of receptors are Ste2 and Ste3, and why is it importaant for the functionality of the cell

Answer 14

G-protein coupled receptors= signalling cascade
part of the marking of the site of budding (before decoding and establishment)

Question 15

what is the output of WT (wild-type) PAR proteins in the cell polarity network

Answer 15

mutual antagonism
establishment of opposing and complementary membrane domains that define a cell’s axis of polarity§

Question 16

where was this PAR protein network first found in

Answer 16

C.elegans

Question 17

example of polarisation in C.elegans after the entry of sperm into the oocyte

Answer 17

Position of entry defines the posterior region
then it will divide asymmetrically along the anterior/posterior axis
larger anterior cell and smaller posterior
different cell fates
=anterior= ectoderm
posterior= meso-/ endoderm germline

Question 18

mutation in the PAR gene in C.elegans

Answer 18

The divide of the regions- anterior and posterior- become less pronounced, leading to possible identical cells

Question 19

longer name for PAR genes

Answer 19

partitioning defective

Question 20

after fertilisation, the sperm has delivered a key structure to the posterior section of the cell, essential for polarisation of the cell. what is this structure

Answer 20

MTOC, microtubule organising centre

Question 21

what does the MTOC do in the posterior regions of the cell

Answer 21

generates microtubules
microtubules recruit Par1 and Par 2

Question 22

Role of Par1 and Par2 in the posterior domain of the cell?

Answer 22

antagonises the anterior Par proteins
-leading to the accumulation of the ‘anterior Par proteins’ at the anterior cortical domain

Question 23

antagonisation of anterior Par proteins allows the generation of pole definition, what are the anterior Par proteins

Answer 23

Par3/ Par6/ aPKC

Question 24

What is key in the definition of the poles

Answer 24

Phosphorylation

Question 25

what causes the asymmetrical spindle placement (HINT- due to sperm etc.)

Answer 25

Formed microtubules pulling on the anterior cortex causes the shift towards the posterior end

Question 26

in Drosophila, what is the name of the CNS progenitor cells that push through the ectoderm

Answer 26

Neuroblasts

Question 27

Neuroblasts divide multiple times asymmetrically, what is the name of this daughter cell and what 2 cells will rise from this cell

Answer 27

the daughter cell of the neuroblast= ganglion mother cell (as it divides to produce daughter cells too)
-neuron and glial cell

Question 28

during and after delamination of neuroblast, what polarity proteins are found in the stalk and apical region of the cell

Answer 28

Cdc42, Par3 and Par6

Question 29

in the Ganglion mother cell (GMC), factors are transported in the basal direction. 2 factors called Prospero and Stauffen, what do they do in the GMC

Answer 29

regulate expression of specific genes in the GMC
when the GMC divides asymmetrically different fates due to these determinants

Question 30

3 main activities involved in movement of cells=
Protrusion
Attachment
Traction

Answer 30

1. pushing out of the plasma membrane in front of cell
2. actin cytoskeleton inside the cell is attached via proteins across the membrane to substratum
3. Bulk of the cell body is drawn forward, by contraction

Question 31

2 types of protrusion

Answer 31

filopodia and lamellipodia
microspikes or sheet-like broad structures

Question 32

role of Cdc42, Rho and Rac in movement of cells and cell polarity establishment

Answer 32

Cdc42- isotropic growth= filopodia everywhere
Rac- essential for small actin filaments
Rho- stress fibres, cell migration

Question 33

signals triggering cell migration converge on what GTPases

Answer 33

Rho small GTPases