Axon Guidance 3 Flashcards

1
Q

main target for RGC

A

mammals - LGN

tectum

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2
Q

what happens to xenopus eyes during metamorphosis

A

eyes positioned on head change

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3
Q

retinotectal projections in animals with non-overlapping visual fields

A

completely cross chiasm

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4
Q

overlapping vision results in what?

A

ipsilateral tract

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5
Q

first intermediate target?

A

ONH

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6
Q

first to differentiate from neuroepithelial pool

A

RGC

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7
Q

CSPG following RGC differentiation

A

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

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8
Q

RGC permissive growth - neuroepithelial cell

A

NCAM and laminin

regression of CSPG

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9
Q

RGC cell adhesion molecules - examples and what they do

A

N-cadherin, NCAM, neurlin, DCC

interact with CAMS in other axons and glial endfeet - tramlining

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10
Q

what happens to axons if CAMS perturbated?

A

defasciculate

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11
Q

3 other factors which might drive RGC to ONH?

A

shh
slits
ephbs

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12
Q

what guides RGC out of eye?

A

netrins

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13
Q

where is netrin expressed in ONH?

A

retinal surface and throughout its depth

axons express netrin receptor needed for growth cone attraction

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14
Q

netrin deficient mice

A

axon mis-routing within RPE

optic nerve thinner

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15
Q

what does RGC attracted to netrin depend on?

A

cAMP

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16
Q

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

A

laminin

prevent cAMP stimulation

17
Q

addition of laminin to eye - pathfinding

A

aberrant through the ONH

18
Q

slit function at chiasm

A

expression suggest role in confining axon growth within appropriate pathway

19
Q

2 types of cells at optic chiasm

A

radial glial cells

CD44 neurons

20
Q

radial glial cell at chiasm

A

span the diencephalon throughout the chiasm

21
Q

CD44 neurons

A

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

22
Q

CD44 neuron and first retinal axon

A

delimited trajectory

23
Q

what happens if CD44 neurons ablated?

A

perturbs normal retinal axonal growth

24
Q

what do the radial glial cells at midline express?

25
difference between ephrin A and B
``` a = secreted b = membrane bound ```
26
what does early expression of ephrin B do to ipsilateral tract formation?
precocious formation | before metamorphosis ipsilateral tract forms
27
optic tract - retinal axons
first axons = deepest | later axons = more superficial
28
what happens if piece of neuroepitheium in optic tract rotated?
just prior to first axon growth, axon turns 90 degees too
29
Laminin in basement membrane at pial surface
retinal axons grow here - permissive role
30
tenascin - optic tract
one isoform in depper layers | confining axons to superficial pathway
31
possible role for tenascin-R at chiasm
help confine axons
32
what signalling is required for correct targeting to tectum?
FGF
33
block FGF - tectim
axons fail to grow into the tectum | axons bypass tectum or branch to avoid it
34
what also induces abnormal pathfinding at border with tectum?
disturbing formation of heparan sulphate (ECM)
35
main class of molecules for A?P difference in axon growth inhibition
ephrins
36
nasal/temporal retina and anterior/posterior tectum
nasal - posterior, less ephA | temporal - anterior
37
netrin - tectum
expressed in posterior tectum | repel axons
38
sema 3A - tectum
posterior tectum | retinal axons sensitive to sema3A as grow through optic tract
39
what ephrin in d/v mapping of retina?
Ephrin B