Strategies of axon guidance Flashcards
What do COS cells expressing shh do and what can it be blocked by
They attract c axons in explant assay
Cyclopamine
How is c axon guidance disrupted
When Smo is knocked out specifically in c axons
What does cre do
binds to 34 base pair sequences which it can cut and region to another LoxP site
What does floxxing do
Allows you to control whether that gene is in the genome and able to be expressed by controlling when the LoxP sites are exposed to the cre recombinase
What do axons exposed to the ectopic floor plate before reaching the midline do and what does this tell you
Respond by turning
Tells you that the act of crossing the floorplate is changing the way that these axons respond to floor plate cells and netrin
What happens to the hind brain in regards to netrin
They lose attraction to netrin and gain a sensitivity to repellents
What does the roundabout gene (ROBO) encode
A receptor for the inhibitory protein slit
What happens in robo mutants
Slits are no longer detected so all axons go back and forth across the midline
What happens when comm protein is missing
Robo is expressed at high levels in cells that would normally cross the midline and they extend their axons longtidunally
Where is robo1 expressed and what does it detect
Expressed on commisual axons and they detect slits made by the floor plate
What does overexpression of Fas2 lead to
A bypass phenotype where the red and blue axons fail to defasiculate and miss their targets
What does BEAT do
It interferes with the homophilic interactions of cell adhesion molecules and the motor neurons exits the ventral nerve cord
What are the two main types of target selection
Discrete targets “cellular”
Topographic maps “mutlicellular”
What does the stripe assay experiment show
That cells in the posterior tectum makes a non-permissive factor that repels temporal reteinal axons
