Cell adhesion, migration and motility Flashcards
What does failure of cells to migrate cause?
Cell, tissue and organism dysfunction and death
What are the roles of adhesion in development?
1) Sperm to oocyte - to transfer paternal DNA
2) Cells begin to express E-cadheirn (adhesion molecules) –> compaction
3) Differences in adhesion cause cells to divide into 2 groups: Inner cell mass (give rise to embyro) and trophoblast (extra-embryonic)
4) Cell implantation into the cellular wall
What is adhesion needed in neural tissue?
- Loss of adhesion from the dorsal nerual tube to form neural crest cells
- Neural crest cells migrate, so must slightly adhere to substrate (but not too much)
- Neural crest cels aggregate once finished migrating - changing adhesion properties again
What did studies on sponges by Wilson show?
- When the cells are deaggregated, they are still able to reaggregate and reorganise into separate tissues based upon their adhesion
- See regionalisation of tissues
What are L cells?
Cells that do not aggregate (don’t express cadherins)
What can L cells be used for?
How?
To study cadherins:
- Transfect L cells with transgenes that express different cadherins and monitor their behaviour
How cant the L cells organise when transfected with cadherins?
Into different groups with the properties of:
1) Different cadherins
2) Different levels of the cadherin
How do cadherins interact?
Bind homophillically to the same cadherin with the extracellular N terminus
Where does Ca2+ bind to cadherins and what does this cause?
Binds at the hinge region to stabilise the cadherin and allow it to interact (cant interact when no Ca2+ is bound - floppy)
How can cells modulate levels of interaction and adhesion? (2 ways)
1) By the type of cadherin they express
2) By the levels of Ca2+ released into the extracellular environment
How are cadherins organised in the cell?
In arrays:
- In the same cell, interact with partners to form lines
- On neighbouring cells - they are arranged perpendicular
- Highly organised: can be adherent on one side of the cell but not the other
What are the 2 types of cadherins?
1) Classical
2) Non-classical
How many different types of cadherins are there in vertebrates?
Over 100
Where are classical cadherins expressed?
In adherens junctions (holds cells together)
What is the structure of classical cadheirns?
- Single pass transmembrane domain
- Repeated domains
- Extracellular hinges
- N terminus extracellular
What are examples of classical cadherins?
1) E-cadherin (epithelial)
2) N-cadherin (neural)
What is the first cadherin to be expressed in the embryo?
What is this cadherin important for?
E-cadherin
Also important for multicellular function
Where is N-cadherin expressed?
In the neural tube and other tissues
What are non-classical cadherins used for?
Specialised for unique functions
How are non-classical cadherins different to classical cadherins?
- Contain many different domains that mediate other protein-protein interactions
- Can have many transmembrane domains
How are non-classical cadherins similar to classical cadherins?
Still have homology in their domains
What is an important types of non-classical cadherin and where is it present?
Protocadherins in the nervous system
What is the structure of protocadherins?
Has many different isoforms which have occurred through alternative splicing of a single gene
What 2 things are protocadherins involved with?
1) Specifying synapses in the brain - confer complex connectivity
2) Involved in self-avoidance behaviour
