Neuronal Movement/Migration Flashcards
(42 cards)
True or false: Radial glia span from the outer to the inner surface
False: from inner to outer
What is radial migration?
The process where neuroblasts migrate by climbing this scaffold of glia.
When they reach their destination, they stop migrating and differentiation is initiated.
What is tangential migration?
Long distance neuronal migration from the LGE to the cerebral cortex
What is the Rostral migratory stream?
long distance neuronal migration from the SVZ to the olfactory bulb
True or false: Migration of SVZ and LGE cells does not require radial glia.
True
o LGE cells migrate tangentially guided by chemical cues.
o SVZ cells migrate rostrally along astrocytic networks.
What do neurons send axons to do?
Establish connections with their appropriate target neurons. This is important for synapse formation and for neuronal survival.
What is the growth cone?
The only motile part of the axon and has to navigate through a complex climate to reach the target.
The growth cone has to be able to adhere to the route in order to make progress.
Which two kinds of cues allow the growth cone to make a decision about which way to go?
Contact mediated and chemotropic guidance cues that are either attractive or repulsive
What causes the physical movement of the growth cone?
Dynamic polymerisation and breakdown of actin filaments.
What do actin filaments do?
- Surround microtubules
- More dynamic than microtubules
- Drive movement
What do microtubules do?
- extend out through most of the growth cones
- Stabilise new extended structure
What is the filopodium
- Adhesive, dynamic projection of cytosol
- Thin projections
What is the lamellipodium?
- Adhesive, dynamic projection of cytosol
- Sheet like
What do attractive signals do to actin?
Stabilise it, so that they elongate towards the signal rather than collapsing
What do repulsive signals do to actin?
Destabilise it
What is cytochalasin?
It causes shrinking/disruption of actin
Binds to monomeric actin.
Blocks actin polymerization and induces depolymerization of filaments.
What is phalloidin?
It disrupts growth cone movement and steering
Stabilises actin filaments and prevents filament depolymerisation
Binds to polymeric actin
What causes the penetration of axon growth into tissue?
The secretion of proteases that allow the passage of the growth cone
his extension requires microtubules, so when microtubule polymerisation is inhibited axons retract.
How can we measure axon growth?
Photobleaching.
We would expect new cells to be inserted throughout or to replace bleached area, but it was actually found that new cells were added distally (closer to cone).
What are cell adhesion molecules (CAMs)?
Molecules expressed by the growth cone that allow it to move.
It does this by modulating adhesion to the extracellular matrix
Provides general cues
What does laminin do?
It appears to pave many axonal tracts, even if only transiently. Because these are found in multiple places, they can only provide general cues
What is haptotaxis?
A directional cell movement in response to adhesive substrates such as ECM. Guidance by adhesion gradients
What do glycosaminoglycans do?
They appear to impede neural outgrowths. They usually prevent adhesion interactions, and can be used to “hide” adhesion substrate and lose traction, preventing elongation.
What are the 4 types of CAMs?
- Sit in cell membrane and bind molecules in membranes of neighbouring cells, e.g. Ig-CAMs, NCAM.
- Sit in cell membrane and bind molecules in the extracellular matrix, e.g. Integrins
- Localised to specific junctions and bind proteins in similar junctions on neighbouring cells, e.g. Cadherins.
- Links to cytoskeleton + secondary messenger signalling pathways affecting cell behaviour (shape, movement).
