Neuronal Migration

Question 1

How does migration lay down layers of cortex?

Answer 1

earliest to migrate lay down first layer

neurons nearest cortical surface were last to migrate

Question 2

how far can neurons migrate?

Answer 2

up to 5-6mm

Question 3

3 types of migration

Answer 3

neurophilic
gliophilic
biphilic

Question 4

radial glial fibres

Answer 4

bundles of elongated radial glia span entire thickness of cortex

Question 5

do neurons migrate inwards or outwards along glial track?

Answer 5

outwards

Question 6

radial glial - transient or permanent?

Answer 6

transient - migration complete degenerate of form astrocytes or neurons

Question 7

how does gliophilic migration ensure neighbour-neighbour relationships?

Answer 7

pre-formed scaffold imposes lateral restraint on neurons

Question 8

attachments of radial glial fibre

Answer 8

ventricular zone to pial surface

Question 9

neurophilic migration - where do neurons migrate to?

Answer 9

surface of the pons

Question 10

what do purkinje cells have?

Answer 10

large dendritic trees

Question 11

granule cell bodies origin

Answer 11

born in outside of cerebellum, migrates downwards with parallel fibres and neuronal projection to granule cell layer

Question 12

bipolar - granule cells

Answer 12

horizontal process along parallel fibres of previous granule cell - neurophilic

Question 13

tripolar - granule cells

Answer 13

vertical process to shaft of bergmann glial fibre - nucleus migrate through own nerve shaft

Question 14

where is final division of granule cells?

Answer 14

near pial surface

Question 15

golgi epithelial cell

Answer 15

cell body of bergmann glial fibre in purkinje layer

Question 16

depth of parallel fibres and time of differentiation

Answer 16

deepest - first to migrate

closes to pial surface = most recent

Question 17

cell adhesion molecules in biphilic migration

Answer 17

N-CAM = non specific 
NCAM-PSA = selective

Question 18

where is NCAM-PSA not present?

Answer 18

proliferative zone

Question 19

where is NCAM-PSA found?

Answer 19

both cell bodies and leading process of migrating neurons and on bergmann glial radial fibre

Question 20

when is staining fro NCAM-PSA lost?

Answer 20

migration complete and synapses formed then lost

Question 21

antibodies to NCAM-PSA

Answer 21

block granule cell migration

Question 22

other CAMS also involved

Answer 22

NG-CAM and cytotactin

Question 23

anti Ng-CAM

Answer 23

inhibits migration out of external granule layer - early stage of migration
not effective day 1.5-3

Question 24

ab to cytotactin

Answer 24

inhibition effective later on in migration

Question 25

what are Ng-CAM and cytotactin needed for?

Answer 25

Ng-CAM - binding to bergmann glia

cytotactin - migration through molecular layer

Question 26

weaver mice - probelem

Answer 26

cerebellar granule neurons fail to migrate and die in ectopic sites

Question 27

weaver mice - problem with neuron on glia?

Answer 27

co-culture normal and weaver tissue - normal neurons migrate on normal and weaver glia
weaver neurones do not migrate
neuronal adhesion defective

Question 28

ventricular zone cell coupling

Answer 28

about 90 cells coupled by gap junctions

Question 29

what do cells from same proliferative area use?

Answer 29

same radial glial guide

Question 30

what do cells in same proliferative zone form?

Answer 30

ontogenetic columns

Question 31

Lissencephaly

Answer 31

smooth cortex, normal thickness but reduced area

Question 32

number of ontogenetic columns in lissencephaly

Answer 32

reduced

Question 33

number of neurons in each column - lissencephaly

Answer 33

normal

Question 34

cause of lissencephaly

Answer 34

early defects (first 7 weeks) when proliferating units being formed

Question 35

polymicrogyria

Answer 35

cortex convuluted but much thinner and normal area

Question 36

ontogenetic columns and number of neurons in polymicrogyria

Answer 36

normal columns

less neurons per column - think

Question 37

week polymicrogyria occur

Answer 37

after week 7

Question 38

cause of polymicrogyria

Answer 38

defective neuronal migration

Question 39

radiation - appearance of brain

Answer 39

small, thin brain much of superficial layers missing, compromised migration

Question 40

interesting finding of irradiated brains

Answer 40

ectopic neurons survive in wrong places
subcortical close to ventricles - proliferative area
never migrated but survived and made incorrect synpases

Question 41

experimentally irradiated rats

Answer 41

survival of ectopic neurons - some still project down spinal cord (part of cortico-spinal projection)
accurately directed axonal growth to synapse with correct spinal targets