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Advanced molecules, membranes and cells > Axon Guidance 2 > Flashcards

Axon Guidance 2 Flashcards

1
Q

What does actin growth or retraction depend on?

A

balance of actin polymerisation and depolymerisation

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2
Q

examples of chemoattractive cues

A

netrins or neurotrophins

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3
Q

active/permissive physical cues

A

ECM or cell adhesion

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4
Q

inhibitory or repulsive physical cues

A

ECM or myelin

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5
Q

trophic support

A

NGF for survival

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6
Q

target derived substrate-bound inhibitory gradients

A

ephrins

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7
Q

chemorepulsive cues

A

MAG or semas

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8
Q

Ig superfamily of cell adhesion molecules

A

CAMs

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9
Q

cadherins

A

cell adhesion molecule

N-cadherin nervous system

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10
Q

what links cadherins to cytoskeleton?

A

catenins

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11
Q

what does N-cadherin depend on?

A

calcium

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12
Q

DO cadherins bind homophiliclaly or heterophilically?

A

homophilically

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13
Q

what do ECM molecules bind to?

A

integrin receptors

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14
Q

examples of ECM molecules

A

laminin
fibronectin
tenascin
proteoglycans - CSPG

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15
Q

how many netrin receptors?

A

4 - DCC, unc5, neogenin and adenosine A2br

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16
Q

what netrin receptors for attraction?

A

DCC multimerisation

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17
Q

what netrin receptor for repulsive properties?

A

cis-binding of unc5

18
Q

how does netrin-DD result in attraction?

A

activation of RhoGTPases cdc42 and rac

19
Q

A2bR - complex, function

A

complex with DCC or netrin binds alone
block receptor prevent netrin induced growth cone guidance
activate adenylate cyclase - stimulation of cAMP

20
Q

what to slits tend to do to axons?

A

repulsion

21
Q

slit/robo mediated repulsion

A

GAP inactivation of cdc42
antagonism of Ena
silence netrin-DCC

22
Q

what do semaphorins bind to?

A

neuropilin/plexin complexes

23
Q

what class of semas require neuropilin co-receptor?

A

3

24
Q

How many semaphorins and families?

A

over 30, 8 subfamilies

all have conserved sema domain

25
Q

class 4 semas

A

PAK activated
inhibit myosin and cofilin by LIMK
growth cone extension
Rho A - repulsion

26
Q

how do class 3 semas work

A

Rho pathway - LIMK activate cofilin and repulsion

can be overriden by blocking LIMK

27
Q

myelin proteins - what are they and their receptors?

A

Nogo, MAG, OMgp

Nogo receptor and p75 co-receptor

28
Q

NOgoA

A

NOgo-66 due to 66 aa sequence

29
Q

what ganglioside is involved in mediating MAG effects?

A

Gt1b

30
Q

what happens following p75 activation by myelin ligands?

A

rhoA activation

growth cone inhibition

31
Q

guidepost cells - sema2

A

d/v and distal/proximal gradients
initial axon growth to CNS
perturbation of sema2 or ROCK - pathfinding errors

32
Q

guidepost cells - sema 1

A

perturbation = pathfinding errors

axons still travel in correct general direction

33
Q

inhibitory factors expressed by roofplate

A

BMP, slits, ephrins, semas, proteoglycans

34
Q

what attraction for commissural neurons is expressed at floorplate?

A

netrins

35
Q

why do axons not cross floor plate again?

A

robo expression increases due to protein - commissureless in invertebrates not known in humans
robo silence netrin-DCC

36
Q

when is axon regeneration across DREZ not possible?

A

few days after birth

oligodendrocytes, myelin

37
Q

peripheral nerve injury

A

wallerian degeneration
schwann cells and mo
cytoskeleton degenerates
tube of schwann cells remain

38
Q

astrocytic scar

A

myelin, proteoglycans, netrin - repulsive in adults axons

39
Q

what happens to cAMP in delvelopment?

A

downregulated

40
Q

cAMP in embryos

A

bind Epac - attraction preferentially

bind PKA little repulsion

41
Q

cAMP in adult

A

bind PKA preferentially

no Epac mediated attraction

42
Q

what happens to neuropilin/plexin receptors in development?

A

upregulated
early embryonic growth cones unaffected by sema3A
receptors - collapse

Advanced molecules, membranes and cells (20 decks)

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