L11 GOK Flashcards
To what receptor do ephrins bind ? What class interact with which receptors ?
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.
What type of proteins does the semaphorin family include?
secreted and membrane-associated proteins
Semaphorin 1A and 3A functions
1A - transmembrane - directs sensory axons in limb development
3A - secreted - repels axons in brain extracts
what happens to axons in SEMA 3A-/- ?
defasiculations - branching to where they normally wouldnt grow
Receptors for semaphorins?
plexin family of transmembrane receptors
9 different plexin receptors in vertebrates
many transmembrane and some secreted semaphorins bind plexin
what happens when SEMA 3A binds plexin and co-receptor neuropilin ?
activation of intracellular
signalling results in the
local disassembly of
GCs cytoskeleton
SEMA 3B acts as an attractant for one subset of neurons and a repellent for another where ?
anterior commisure
Sema 3A is an attractant for what and a repellent for what of cortical dendrites ?
attracts - axons
repels - dendrites
What signalling switches Sema3A repulsion to attraction ?
cGMP signalling
what are slits ?
large axon repellents that stimulate axon and dendrite branching
how many slit genes in mammals ?
3 genes
what are ephrins ? what are the subfamilies?
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.
topographic projections meaning ?
ordered arrangement of axons in a given field
what are the 3 key morphogen families that impact axon guidance ?
HH
BMP
Wnt
what do morphgens to at early stages in development ?
they specify cell fate
what do growth factors regulate what at later stages of development ?
survival
some play an earlier role in axon guidance
HGF, FGF, GDNF guide which axons ?
Neurotrophins (BDNF and NT3) guide ?
Neurogulins guide ?
motor neuron
sensory
thalamocortical
example of growth factor that stimulates branching in thalamocortical neurons ?
BDNF
Growth factors involved in which type of guidance of axons?
attractive guidance
What do growth cones do in response to guidance cues ?
turn , extend or retract
forward-crawling motion of GC invovles 4 steps …
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
where is microtubules and actin located in GC?
microt’s - in axon shaft and central domain
actin - filopodia and peripheral domain
what does treadmilling mech in GC involve ?
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
Semaphorin, receptor stimulate what in the GC
activate Rho via
an adaptor protein that stimulates
exchange of GDP for GTP on the
GTPase
