Axon Guidance Flashcards
What is the receptor for slit?
Robo
What is the receptor for ephrins?
Eph
What is the receptor for semaphorins?
Plexins
Neuropilin and plexin complexes
What is the receptor for VEGF-A?
NRP1
VEGFR2
What is the effect of Robo and in which neuron type does this occur?
Growth cone repulsion
In spinal commissural neurons
What is the effect of ephrins?
Reverse signal - growth cone survival
What is the effect of Eph?
Forward signal - growth cone collapse
In which neuron type does Eph/ephrin signalling occur?
Spinal MNs
What is involved in the neuropilin and plexin complex that binds semaphorins?
NRP1/2
PLXNA1-4
What is the effect of semaphorins?
Growth cone repulsion
Which semaphorin binds PLXNB1 directly without neuropilin?
SEMA3E
What is the effect of SEMA3E binding to PLXNB1 without recruiting NRP1 and VEGFR2, and where does this occur?
Growth cone repulsion
In cortical axons
What is the effect of SEMA3E binding to PLXNB1 and recruiting NRP1 and VEGFR2, and where does this occur?
Axon growth
In subicular axons
Which other ligand can NRP1 bind, what is its effect, and where does this occur?
VEGF-A
Growth cone attraction and axon growth
In retinal ganglion cell (RGC) axons
What is the effect of VEGF-A binding to VEGFR2 and where does this occur?
Growth cone attraction and axon growth
In commissural axons of spinal cord
Which receptor types does SEMA3A bind to and what are their effects?
Mainly Plxna4 - repel
Assisted by Plxna3 - slightly repel
Which guidance cue and receptor control Drosophila midline crossing?
Slit/robo
What is expressed by Drosophila midline glia?
Slit
What is expressed by Drosophila non-crossing axons?
Robo
What is the effect of the loss of function of Robo in Drosophila?
Axons recross midline
What is the effect of a lack of Slit1/2/3 in mice?
Disorganised central commisure of spinal cord midline - all axons cross over at midline
Where are slits not expressed in the mouse spinal cord?
Mouse chiasmatic midline
Which guidance cue and receptor promote ipsilateral RGC projection?
Eph/ephrin
Where is ephB1 expressed in mice?
Ventrotemporal crescent - where ipsilaterally-projecting neurons originate
What is the effect of ephB1 KO in mice?
Loss of ipsilateral projection - loss of stereovision
Where is ephrin B2 expressed?
Chiasm where axons cross
What is the effect of ephrin B2 KO in mice?
Fewer ipsilateral projections
Embryonic lethal
Name a marker for contralaterally-projecting RGCs
NRP1
Name a marker for ipsilaterally-projecting RGCs
ZIC2
What is the effect of Nrp1 KO in mice?
Defasciculation after crossing
Increased ipsilateral projections
What is the negative signal to promote ipsilateral projection?
EphrinB2
What is the positive signal to promote contralateral projection?
VEGF164
