7 - Cell Polarity II Flashcards
What hypothesis is the basis of modern day developmental genetics?
Cell can generate daughters that are intrinsically different.
What are the 2 main routes in which sister cells can have different fates?
1 - The mother cells could divide to generate daughters that have inherited different components.
2 - Daughters could be equal and birth and become different due to exposure to different environmental signals.
What are some important steps in generating polarity and cell fate decisions?
- Establishing the axis of polarity
- A mitotic spindle positioned along the axis
- Cell fate determinants distributed differentially to the daughter cells.
What is the role of PAR proteins in cell polarity networks?
They form the core.
What is the output of cell polarity networks?
One of mutual antagonism with the establishment of opposing and elementary membrane domains.
What happens in the early development of c.elegans?
A series of asymmetric cell divisions.
When does polarisation start?
When the sperm enters the oocyte.
What does the position of entry of the sperm define?
the posterior end of the zygote or the PO cell.
What does the zygote/PO cell do after sperm entry?
It divides asymmetrically along the anterior-posterior axis - This produces a large anterior cell (AB) and a smaller posterior cell (P1).
Where did the discovery of PAR genes come from?
genetic screening to identify key players in the asymmetric division.
When in symmetry broken in cells?
On fertilisation when the sperm delivers the microtubule organising centre (MTOC), which becomes the posterior pole and so defines the axis of polarity.
Why are Par1 and Par2 recruited?
To antagonise the anterior Par proteins resulting in the distinct localisations of the par proteins.
What Par proteins are at the anterior cortex?
Par3, Par6 and aPkc
What Par proteins are at the posterior cortex?
Par1 and Par2
what are neuroblasts?
Progenitor cells
Where are neuroblasts found?
Within a specific region of an epithelial monolayer called the ventral neuroectoderm.
How do the neuroblasts move from their position?
They delaminate and undergo repeated rounds of cell division. Which gives rise to a ganglion mother cell (GMC) and a larger atypical daughter cell.
What does the ganglion mother cell divide to give rise to?
A neuron and a glia cell the apical daughter cell continues to divide.
When is polarity established?
When the cell is still in the neuroectoderm layer.
What happens when the neuroblasts delaminate?
Cdc42, Par3 and Par6 are found in a stalk that continues to extend to the epithelium.
How does most animal locomotion occur?
The cells crawl on the surface of a solid substrate.
What are the 3 main activities required for movement?
Protrusion, Attachment and Traction.
Protrusion is…
Pushing out of the plasma membrane in front of the cell.
Attachment is…
When the actin cytoskeleton in the cell is attached via interacting proteins.
Traction is…
the bulk of the cell body being drawn forward through a process of contraction.
What are filopodia?
Micro-spikes which contain a core of actin bundle filaments.
What are lamellipodia?
Short branch structured actin.
What are stress fibres?
Bundles of actin filaments involved in the contractility required to move the body of the cell forward.
What does cell polarity establishment in cell migration involve?
Small Rho GTPases - cCdc42, Rac, Rho.
What is chemotaxis?
the movement of cells towards or away from a signal such as a diffusible chemical. eg the movement of neutrophil towards the site of bacterial infection.
What is the first tissue that emerges during development?
Epithelium.
Where does the apical side of the epithelium face?
The external environs.
Where does the basal side of the epithelium face?
The basement membrane.
what does the polarised cytoskeleton of actin help with?
It allows for the apical surface to constrict, which is also important for gastrulation and tubulation.
What is epithelial mesenchymal transition (MET)?
The rapid loss of epithelial phenotype.
What is mesenchymal epithelial transition?
the reacquisition of epithelial phenotype.
What is epithelial mesenchymal transition important for?
Development, it is also important in cancer metastasis
