L11 GOK

Question 1

To what receptor do ephrins bind ?
What class interact with which receptors ?

Answer 1

EphA and EphB - receptor tyrosine kinase

Class A ephrins interact with five class A Eph receptors.
- class B ephrins interact with three class B Eph receptors.

Question 2

What type of proteins does the semaphorin family include?

Answer 2

secreted and membrane-associated proteins

Question 3

Semaphorin 1A and 3A functions

Answer 3

1A - transmembrane - directs sensory axons in limb development

3A - secreted - repels axons in brain extracts

Question 4

what happens to axons in SEMA 3A-/- ?

Answer 4

defasiculations - branching to where they normally wouldnt grow

Question 5

Receptors for semaphorins?

Answer 5

plexin family of transmembrane receptors
9 different plexin receptors in vertebrates

many transmembrane and some secreted semaphorins bind plexin

Question 6

what happens when SEMA 3A binds plexin and co-receptor neuropilin ?

Answer 6

activation of intracellular
signalling results in the
local disassembly of
GCs cytoskeleton

Question 7

SEMA 3B acts as an attractant for one subset of neurons and a repellent for another where ?

Answer 7

anterior commisure

Question 8

Sema 3A is an attractant for what and a repellent for what of cortical dendrites ?

Answer 8

attracts - axons

repels - dendrites

Question 9

What signalling switches Sema3A repulsion to attraction ?

Answer 9

cGMP signalling

Question 10

what are slits ?

Answer 10

large axon repellents that stimulate axon and dendrite branching

Question 11

how many slit genes in mammals ?

Answer 11

3 genes

Question 12

what are ephrins ? what are the subfamilies?

Answer 12

cell surface molecules that act as guidance cues
2 subfamilies:
1) 8 class A ephrins - tethered to the cell surface via GPI linkages.

2) 6 class B - ephrins are transmembrane molecules.

Question 13

topographic projections meaning ?

Answer 13

ordered arrangement of axons in a given field

Question 14

what are the 3 key morphogen families that impact axon guidance ?

Answer 14

HH
BMP
Wnt

Question 15

what do morphgens to at early stages in development ?

Answer 15

they specify cell fate

Question 16

what do growth factors regulate what at later stages of development ?

Answer 16

survival

some play an earlier role in axon guidance

Question 17

HGF, FGF, GDNF guide which axons ?
Neurotrophins (BDNF and NT3) guide ?
Neurogulins guide ?

Answer 17

motor neuron
sensory
thalamocortical

Question 18

example of growth factor that stimulates branching in thalamocortical neurons ?

Answer 18

BDNF

Question 19

Growth factors involved in which type of guidance of axons?

Answer 19

attractive guidance

Question 20

What do growth cones do in response to guidance cues ?

Answer 20

turn , extend or retract

Question 21

forward-crawling motion of GC invovles 4 steps …

Answer 21

1) extension of the leading edge,
2) attachment to substrate,
3) traction-generating mechanism that creates tension which draws GC forward
4) retraction of unattached processes

Question 22

where is microtubules and actin located in GC?

Answer 22

microt’s - in axon shaft and central domain

actin - filopodia and peripheral domain

Question 23

what does treadmilling mech in GC involve ?

Answer 23

continuous rearward flow of polymerized
actin away from leading edge toward central domain

readmilling due to myosin-based motors driving F-actin toward central domain

Question 24

Semaphorin, receptor stimulate what in the GC

Answer 24

activate Rho via
an adaptor protein that stimulates
exchange of GDP for GTP on the
GTPase

Question 25

Eph and robo receptors inhibit/ stimulate what in the GC

Answer 25

Rho via adaptor via

an adaptor protein

Question 26

netrin receptor DCC activates what inthe GC

Answer 26

Rac

Question 27

how do guidance cues reg microtubule dynamics ?

example?

Answer 27

through microtubule binding proteins

CLASP and APC

Question 28

where do the MBP bind on microtubules ?

Answer 28

distal end

Question 29

how does slit reg microtubules ?

Answer 29

replusion by actiavtes CLASP stabilizes
microtubules and prevents their extension
into GC periphery.

Question 30

how does NGF reg microtubules ?

Answer 30

mediates neurite outgrowth - esults
from APC regulation, which promotes
microtubule assembly and extension into
GC periphery