Lecture 6 - Growth and Guidance of Axons II Flashcards
How is adhesion converted into directional cues in the growth cone?
changes in the level of intracellular regulatory proteins determine whether the same extrinsic cue will attract or repel a growth cone - calcium gradient cAMP PKA protein synthesis for new factors
When is the growth cone repelled by netrin?
when PKA and cAMP is low
When is the growth cone attracted to netrin?
when cAMP and PKA is high
What is a brief overview of the frog visual system?
lens projects an inverted visual image onto the retina and the optic nerve then transfers the image with an additional inversion to the optic tectum
Where do anterior neurons and posterior neurons project to in the frog?
AN —-> Posterior tectum
PN —–> anterior tectum
What is the Frog experiment?
-cut the optic nerve so the axons regenerate and stain the axons; but the axon and take the eyeball of the frog and invert it 180 degrees
-if chemical cues the axons will grow in opposite direction meaning anterior will grow to anterior and posterior will go to posterior because the anterior is now posterior
-if activity everything will be the same because they are getting the same info in every direction
-had a behavior - if vision is inverted the frog will look at the fly in the air and stick tongue out on the ground cause is 180 degrees inverted
What 6 major types of extracellular cues guide growth cones?
- ECM adhesion - laminin
- cell surface adhesion -adhesion to other neurons or axons
- fasciculation - adhere to pioneer neurons
4.chemoattraction - soluble chemical signals induce attraction - contact inhibition - cell surface repellant cues
- chemorepulsion -soluble chemical signals induce repulsion
What diverse molecular families control the growth and guidance of developing axons?
- cadherins - promote adhesion
- immunoglobulin domain containing proteins
- ephrins - heterotypic interactions
- laminins - ECM binding protein via integrins
- semaphorins - dendrites released as a concentration gradient
- slits - robo receptor - repulsion
- netrins - attraction or repulsion
What are commissural neurons?
convey sensory info from the spinal cord to the brain at the ventral midline of the spinal cord across the floor plate
What causes the commisural neurons to go from dorsal to ventral to the floor plate and cross the midline?
netrin secreted by ventral midline cells
What directs axons away from the dorsal roof plate?
BMPs
What attracts axons to the floor plate?
netrin-Dcc signaling
What prevents recrossing of the midline?
slit-robo
What causes the axons to turn and travel rostrally to the brain?
wnt gradient
Are netrins secreted by the floorplate to mediate chemoattraction?
yes via chemotaxis not haptotaxis where the neurons are physically touching crumbs of netrin
Summary
