Axon Guidance 3

Question 1

main target for RGC

Answer 1

mammals - LGN

tectum

Question 2

what happens to xenopus eyes during metamorphosis

Answer 2

eyes positioned on head change

Question 3

retinotectal projections in animals with non-overlapping visual fields

Answer 3

completely cross chiasm

Question 4

overlapping vision results in what?

Answer 4

ipsilateral tract

Question 5

first intermediate target?

Answer 5

ONH

Question 6

first to differentiate from neuroepithelial pool

Answer 6

RGC

Question 7

CSPG following RGC differentiation

Answer 7

differentiate just dorsal to ONH
CSPG regress from this point
nudge towards ONH

Question 8

RGC permissive growth - neuroepithelial cell

Answer 8

NCAM and laminin

regression of CSPG

Question 9

RGC cell adhesion molecules - examples and what they do

Answer 9

N-cadherin, NCAM, neurlin, DCC

interact with CAMS in other axons and glial endfeet - tramlining

Question 10

what happens to axons if CAMS perturbated?

Answer 10

defasciculate

Question 11

3 other factors which might drive RGC to ONH?

Answer 11

shh
slits
ephbs

Question 12

what guides RGC out of eye?

Answer 12

netrins

Question 13

where is netrin expressed in ONH?

Answer 13

retinal surface and throughout its depth

axons express netrin receptor needed for growth cone attraction

Question 14

netrin deficient mice

Answer 14

axon mis-routing within RPE

optic nerve thinner

Question 15

what does RGC attracted to netrin depend on?

Answer 15

cAMP

Question 16

in the presence of what are growth cones repelled by netrin?

Answer 16

laminin

prevent cAMP stimulation

Question 17

addition of laminin to eye - pathfinding

Answer 17

aberrant through the ONH

Question 18

slit function at chiasm

Answer 18

expression suggest role in confining axon growth within appropriate pathway

Question 19

2 types of cells at optic chiasm

Answer 19

radial glial cells

CD44 neurons

Question 20

radial glial cell at chiasm

Answer 20

span the diencephalon throughout the chiasm

Question 21

CD44 neurons

Answer 21

v shaped wedge express L1 and CD44 to promote or inhibit axon growth

Question 22

CD44 neuron and first retinal axon

Answer 22

delimited trajectory

Question 23

what happens if CD44 neurons ablated?

Answer 23

perturbs normal retinal axonal growth

Question 24

what do the radial glial cells at midline express?

Answer 24

ephrins

Question 25

difference between ephrin A and B

Answer 25

a = secreted 
b = membrane bound

Question 26

what does early expression of ephrin B do to ipsilateral tract formation?

Answer 26

precocious formation

before metamorphosis ipsilateral tract forms

Question 27

optic tract - retinal axons

Answer 27

first axons = deepest

later axons = more superficial

Question 28

what happens if piece of neuroepitheium in optic tract rotated?

Answer 28

just prior to first axon growth, axon turns 90 degees too

Question 29

Laminin in basement membrane at pial surface

Answer 29

retinal axons grow here - permissive role

Question 30

tenascin - optic tract

Answer 30

one isoform in depper layers

confining axons to superficial pathway

Question 31

possible role for tenascin-R at chiasm

Answer 31

help confine axons

Question 32

what signalling is required for correct targeting to tectum?

Answer 32

FGF

Question 33

block FGF - tectim

Answer 33

axons fail to grow into the tectum

axons bypass tectum or branch to avoid it

Question 34

what also induces abnormal pathfinding at border with tectum?

Answer 34

disturbing formation of heparan sulphate (ECM)

Question 35

main class of molecules for A?P difference in axon growth inhibition

Answer 35

ephrins

Question 36

nasal/temporal retina and anterior/posterior tectum

Answer 36

nasal - posterior, less ephA

temporal - anterior

Question 37

netrin - tectum

Answer 37

expressed in posterior tectum

repel axons

Question 38

sema 3A - tectum

Answer 38

posterior tectum

retinal axons sensitive to sema3A as grow through optic tract

Question 39

what ephrin in d/v mapping of retina?

Answer 39

Ephrin B