Axonal outgrowth during development Flashcards
What are the most important mechanisms controlling axonal outgrowth?
- Contact attraction
- Contact repulsion
- Autocrine mechanisms
- Chemoattraction
- Chemorepulsion
When is axonal outgrowth happening?
During development
After trauma (regeneration)
In plasticity (remodeling of neuronal connections)
What are neurites?
Common term for axons and dendrites
What are the four stages of neurite (axon+dendrite) development?
1) Lamelipodia formation
2) Neurite formation
3) One neurite become an axon
4) The other neurites become dendrites
What is the morphology of dendrites vs axons?
Dendrites are very branched, axons are longer but not as branched.
Where do you most often find exitatory synapses? and inhibitory?
On spines.
Inhibitory are often on the cell body.
What is a growth cone?
The growth cone is the axon tip.
Growth cones interpret environmental signals and act as motor structures.
What cellular component is most important for outgrowth of the growth cone?
Filopodia, made by F-actin.
The F-actin polymerisation provides the motility of the growth cone.
What source of mechanical force is important for axonal growth?
The connection between the extracellular matrix and the intracellular cytoskeleton
What gives the axon the mechanical force, leading its outgrowth?
Actin monomers being transported to the tip where they polymerise
What determines in what direction an axon will grow?
Stereotropism, cell contact and guidance and chemotropic signals.
The respons to certain signals will be determine by the receptors on the growth cone.
What are the four most common neurotropic factors and their receptors?
NGF, BDNF, NT-4 and NT-3.
TrkA, B and C.
How does NFG signals in a medium affect neurites (dendrites+axons)?
It promotes local branching
What is the function of the Rho family GTPases in axon growth?
They regulate the actin cytoskeleton
Almost all inhibitors of axonal growth act through…?
RhoA
Almost all stimulators of axonal growth act through…?
Cdc41 and Rac
What is the relation between axonal growth and myelination?
Myelin inhibits axonal growth.
In early development there is high possibility for axonal growth, once neurons are myelinated, growth decreases.
What EM proteins inhibit axonal growth?
Semaphorins, chondroitin sulfate proteoglycans (CSPGs) and tenascin
How does extracellular proteins guide axonal outgrowth?
Multiple different types of extracellular proteins create physical barriers, and inhibit growth via signals, when axons contact them. This avoids axons growing into the wrong areas.
Via what protein, does CSPCs signal growth inhibition to axons?
RhoA
(and others)
