Establishment of Cell Polarity Flashcards
What is a good system for studying the acqusition of cell polarity?
The fucous zygote
What shape is the zygote of the fucus at 0 hours?
Apolar (spherical)
What shape is the zygote of the fucus at 12 hours?
Pear shaped
What happens to the zygote of the fucus at 24 hours?
The first cell division takes place at a right angle to the axis of symmetry
What are the two parts of the fucus zygote?
The thalus (The bit bulb bit) and the rhizoid (the wee tail)
Name 5 enviromental facotrs involved in determining cell polairity?
- Light
- Temperature
- PH and Salt
- Electrical gradient
- Fertilisation
How is light involved in estabilishing cell polairity in the fucus?
The Rhizoid develops on the shaded side
At which point in the fucus is polairity fixed?
After 12 hours - before that you can move light and it will change the polairity
How is feritlization involved in stablishing cell polarity?
When the sperm enters whatever point this is will become the rhizoid
How is heat involved in establishing cell polarity?
The rhizoid will grow on the warm side
How are ph and salt involved in establishing cell polairity in the fucus?
The rhizoid grows to the alkaline ph and the higher salt concentration
How is an electrical gradient involved in cell polarity?
The rhizoid will grow at the negative end
What does the fact that rhizoid grows at the negative end and the thalus at the positive end when an electrical gradient is applied?
That development of the fucus involves ion gradients and movements
How is calcium involved in establishing cell polarity?
There is ca2+ ion efflux at the thalus end which causes it to be negative which is why it is attracted to the positive end of the electrical gradient. At the rhizoid end there is a localisation of calcium ion channels causing calcium influx and that end of the cell to be positive which means it is attracted to the negative end of the electrical gradient
Some zygotes already have asymmetry; why is this?
due to localised cytoplasmic determinants
How are localised cytoplasmic determinants involved in determining cell fate?
The distrubutuon of these in different cells causes different cells to become different things
What are two good systems for studying localised cytoplasmic determinants?
Amphibians and ascidians (sea squirt)
Why is the ascidian (Sea squirt) a good model for cytoplasmic determinant study?
Because it is coloured depending on what cytoplasmic regions are in it and these regions go on to become different tissues so you can see what the cytoplasmic determinants functions are
How could you test that it was the cytoplasmic determinants in this region that cause it to turn into the tissue it does?
Transplant these in a different region of the cell to see if that tissue forms there
What do local cytoplasmic determinants establish in drosophillia>
The anterior posterior axis
At what point in drosophillia development does establishment of the anterior-posterior axis by LCDs occur?
In the oocyte
What is isthe dros oocyte surrounded by?
Nurse cells
What do nurse cells do?
They synthesised macromolecules (mRNA proteins) and transfer them to the oocyte via cytoplasmic bridges
What is a macromolecule that nurse cells transfer to the oocyte in order to establish anterior-posterior axis?
Bicoid mRNA
What does the end that bicoid mRNA is localised at become?
The anterior end
How can you tell that bicoid is a localised cytoplasmic determinant involved in anterior development?
Because in a bicoid mutant (has no bicoid mRNA) two posterior ends develop
How is the bicoid protein localised at the anterior pole?
It is transferred to the oocyte in the mRNA form from the nurse cell where is is transcribed in the anterior pole in the bicoid protein which can then regulate the development of the anterior end
What is bicoid an example of ?
A maternal effect gene
What is a maternal effect gene?
A gene that is transcribed by the parent/mother cell and it then transferred to the oocyte
What are the two maternal effect genes that regulate production of anterior structures?
Bicoid and Hunchback
What are the two maternal effect genes that are involved in regulation of the posterior structure prodocution?
Nanos and Caudal
What kind of proteins are hunchback, bicoid and caudal?
Transcription factors
Where is the bicoid mRNA localised?
The anterior end
Where is the nanos mRNA localised?
The posterior end
Where are caudal and hunchback mRNA localised?
They are not localised all throughout the structure
What causes caudal mRNA to only be transcribed at the posterior end?
Bicoid inhibits it at the anterior end
What causes hunchback to only be trancribed at the anterior end?
Nanos inhibits it at the posterior end
