L4- Cell Movements in Development Flashcards
What makes up the cytoskeleton?
Microtubules- columns of alpha and beta tubulin dimers
Actin filaments- actin subunits
Intermediate filaments- various protein subunits
What is the role of actin?
Cell motility and shape
Can work with myosin to produce contraction as part of a contractile network/movement of organelles
Can change shape by polymerising into actin bundles
What is cell migration?
The independent movement of cells through or over other tissues or non-cellular substrates.
What are the steps in cell migration?
- Protrusion of the leading edge
- Adhesion at the leading edge
- De-adhesion at the trailing edge
- Movement of cell body
What are lamellipodia and fillopodia?
Actin rich
Extend cell in particular direction
Found at the leading edge of migrating cells
Protrusions may sense cells environment
What is the epithelial-mesenchymal transition?
When neural crest cells delaminate from the neural tube and lose their epithelial organisation to take on a migratory, mesenchymal organisation
How to neural crest cells only migrate through the anterior half of the somites?
Cells in posterior half express repulsive signals ephrin and semaphorin-3F on their surface
Neural crest cells express Eph and neuropilin-2 receptors (bind respectively)
Receptor activation generates ‘keep out’ signal so cells stay in the anterior half of somites.
How does a sheet of cells move?
Apical constriction- localised contraction of cells apical surfaces in epithelia via actomyosin network, takes place at 3 ‘hinge points’ in cells
Cuboidal cell profile becomes wedge shaped and cell adhesion (CAMS) holds cells in a sheet
How does apical constriction occur in neurulation?
The neural tube forms via the folding of the neural plate and is driven by apical constriction
The neural plate is continuous with the non neural ectoderm but at the end of neurulation a fusion event closes the tube and separates it
What is mediolateral intercalation?
When cells exchange places with eachother within the same place
Allows convergent extension during gastrulation to elongate body axis of embryo
What is cell intercalation?
Change of shape of a group of cells
What is radial intercalation?
Reduction in depth of a tissue
What is mediolateral intercalation?
Elongate and narrow a tissue
