neuron migration and motility

Question 1

types of neuron migration

Answer 1

gliophilic migration
neurophilic migration
biphilic migration

Question 2

radial migration

Answer 2

gliophilic migration

radiate away from centre where they were born

Question 3

tangential migration

Answer 3

neurophilic migration

follow contours of cortex, and run parallel to them

Question 4

ex of neurons using neurophillic migration

Answer 4

interneurons emerging from the medial ganglionic eminence

Question 5

granule cells of the cerebellum - development

Answer 5

embryonic
- GCs originate at rhombic lip and migrate to proliferative zone
- frist vision of GC near suffice membrane
- become bipolar by extending horizontal processes along parallel fibres of other GCs (neurophilic migration)

postnatal
- bipolar neurophilic extension continues
- become bipolar and migrate inwards from PZ
- vertical process attaches onto shaft of Bergman glia (gliophilic migration)
- once vertical process sufficient length the nucleus migrates through its own nerve shaft
- successive generations guided by same BG

Question 6

what mechanism allows granule cells to have neurophilic and gliophilic migration

Answer 6

certain populations of cell adhesion molecule (NCAM-PSA) binding to glia and neurite changing over time

Question 7

Weaver mice

Answer 7

natural mutation - ataxia, uneven gait

abnormal granule cell migration - can’t bind to Bergman glia

Question 8

radial units

Answer 8

groups cells in ventricular PZ, coupled by gap junctions
come from same area and use same radial glial cells to reach cortex

if environmental insult early one, some columns may die off
if environmental insult later time point, cells may be prevented from migrating

Question 9

lissencephaly

Answer 9

early defects when proliferating units are forming proliferating zone (first 7 weeks gestation)

number columns greatly reduced, normal number of cells in each

Question 10

polymicrogyria

Answer 10

much thinner cortex

normal number of columns but much less neurons in each
defect after number of units formed - after first 7 weeks gestations

defect in neuron migration

Question 11

microtubules support bidirectional transport

Answer 11

2 organelles pass each other going opposite directions - separate tracks on single MT

kinesin supports anterograde forward movement
dynein mediates retrograde movement

these molecules can be on same track and pass each other

Question 12

how is retrograde flow of actin driven

Answer 12

1) coupled to ATP
actin flow due to high energy phosphates. F actin depoolymersises and becomes G actin, has ADP attached which will be phosphorylated to ATP. Globular actin with ATP comes into contact with barbed end , phosphate is released

2) coupled ot myosin I
myosin molecules attaches to sub membranous structure, requiring ATP. ATP –> ADP and energy drives the power stroke up to left. Lots of myosin molecules doing this contributes to retrograde flow

Question 13

forward movement of actin

Answer 13

actin filament driven backwards by myosin attached to submembranous matrix
talin bound to integrin, which binds to ECM substrate
actin binds to talin and is now stationary due to rigid mechanical interaction with external substrate via integrin/talin complex
myosin and sub membranous matrix must not move forward

“molecular clutch”