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332: Neurobiology > 10. Cell Interactions in Neural Development > Flashcards

10. Cell Interactions in Neural Development Flashcards

1
Q

following neurulation how many population of neurons are specified

A

3

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2
Q

name the 3 populations of neurons specified after neurulation

A
  1. commissural neurons
  2. dorsal root ganglian neurons (sensory neurons)
  3. motor neurons
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3
Q

describe the process of lateral inhibition

A

one cells response to a stimulus is inhibited by excitation of a neighbouring cell

this prevents two cells from acquiring the same cell fate

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4
Q

what inhibits the neural fate in the neuroectoderm

A

notch

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5
Q

what do all cells in the proneural cluster express

A

Acheate-scute proteins

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6
Q

which cell develops into the SOP from the pro neural cluster

A

the one that expresses the most acheate-scute protein

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7
Q

describe the signalling process which is instigated by the one cell that expresses the most acheate-scute

A

acheate-scute activates expression of delta

delta binds to notch (a transmembrane protein)

notch binding activates the enhancer of split proteins which repress the expression of acheate-scute

this produces a positive feedback loop where eventually only one cell expresses delta

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8
Q

what happens to the cells with no delta

A

they become epidermal cells

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9
Q

this positive feedback loop escalates acheate-scute production, what happens next in the SOP

A

levels are high enough to switch on bHLH proteins which commit it as a sensory organ precursor

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10
Q

what drives the movement of the growth cone

A

actin polymerisation/ depolymerisation

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11
Q

describe chemotaxis

A

the growth cone responds to chemical signals to determine the direction of movement

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12
Q

name a chemoattractant

A

netrin

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13
Q

name a chemorepulsant

A

semaphorins

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14
Q

name a contact attraction molecule

A

cadherins

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15
Q

name a contact repulsion molecule

A

ephrins

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16
Q

describe axonal outgrowth in commissural neurons

A

cell bodies send out axons which migrate ventrally through the floor plate to the other side of the neural tube

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17
Q

what does the floor plate produce

A

netrin 1

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18
Q

what two types of netrin are found in vertebrates

A

netrin 1 and netrin 2

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19
Q

what receptor in commissural neurons receives netrin

A

Unc-40

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20
Q

what does Unc-5 do?

A

modifies the response of Unc-40

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21
Q

what happens in neurons expressing unc-40 and unc-5

A

neurons no longer move towards netrin, they change there chemotactic behaviour

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22
Q

what molecule produces clustering of acetylcholine receptors

A

agrin

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23
Q

how many Ach receptors can one molecule of agrin aggregate

A

200 Ach receptors

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24
Q

what does agrin bind to and how does it work

A

binds to LRP4/MUSK which activates raspyn through rho/rac

activates raspyn binds to the AchR resulting in aggregation

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25
Q

which part of the growth cone interacts with its immediate environment

A

the filopodia finger-like projections

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26
Q

where in the neuron is the site of protein synthesis, what is made here

A

the cell body
the components for growth cone extension are made here

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27
Q

how are proteins for neural extension transported to the growth cone

A

by anterograde transport in vesicles along microtubules

28
Q

what are the three domains of the growth cone

A

the central domain
the transitional zone
the peripheral domain

29
Q

what is found in the central domain

A

microtubules, organelles and vesicles

30
Q

what is found in the transitional zone

A

an arch of actin that separates domains

31
Q

what is found in the peripheral domain

A

actin, filopodia and a lamellipodia like veil

32
Q

cell adhesion molecules are important in guiding axon development via contact adhesion, name 2

A

N-CAM
N-cadherin

33
Q

where is N-CAM found

A

on the surface of neurons and glial cells

34
Q

what do N-CAM KO mice show

A

axon migration defects and motor deficits

35
Q

how does cadherins bind

A

vial calcium dependent adhesion at both ends

36
Q

where are substrate adhesion molecules found

A

in the extracellular matrix

37
Q

name 2 substrate adhesion molecules

A

laminin
fibronectin

38
Q

what do laminin and fibronectin in the ECM interact with

A

intern receptors on the cell surface

39
Q

describe the evidence for the axonal growth of commissural neurons

A

if you dissect a spinal cord in two, commissural neurons will still want to send neurons to the bottom towards the floor plate. and they will dangle out

40
Q

what are two receptors for semaphorins

A

neuropillins and plexin

41
Q

what do neuropillins need to work

A

the co receptor plexin is needed as neuropillins have no signal transduction system

42
Q

wha happens once semaphorin binds to plexin

A

microtubules are disassembled, actin is depolymerised and the growth cone collapses

43
Q

give an example of where chemorepulsion occurs

A

in the spinal cord, the ventral part secretes semaphorin 3 to repel incoming thermoreceptor and nociceptor neurites

44
Q

name a contact repulsion

A

ephrins

45
Q

what distinguishes ephrin signalling from other signalling pathways

A

it is bi-directional

46
Q

ephrin signalling is bi-directional, what does this mean?

A

one signal that instructs the growth cone to collapse

another signal that instructs the cell the growth cone has made contact with to change protein expression on the cell surface

47
Q

describe the process of retinotopic map formation

A

nerve cells in the retina send out projections to the tectum.

temporal retinal neurons = high sensitivity to ephrins

nasal retinal neurons = low sensitivity to ephrins and so extend to a higher concentration of ephrins

48
Q

what are pioneer axons

A

pioneer axons are sent first, these use external cues to lay the foundations for future axons

follower axons use these as a pathway

49
Q

what molecule is essential for neurite outgrowth

A

brain derived neurotrophic factor

50
Q

what are the receptors for BDNF

A

tyrosine receptor kinases

51
Q

what happens in cells without neurite growth factor

A

poor neurotic outgrowth and neuronal death

52
Q

what happens when the axon reaches its target

A

the axon converts into synaptic terminal and acetylcholine receptors cluster

53
Q

what 3 molecules does the nerve terminal secrete

A

agrin
aria
acetylcholine

54
Q

what is the role of aria

A

stimulates the production of new Ach receptors

55
Q

what is the role of agrin

A

aggregates ach receptors

56
Q

what is the fancy term for neural tube defects

A

dysraphic defects

57
Q

what and when are dysraphic defects caused

A

occur within the first three weeks of gestation and are caused by incomplete closure of the neural tube.

58
Q

name 2 conditions that are neural tube defects

A

anencephaly
spina bifida

59
Q

describe spina bifida and how it is corrected

A

the spinal cord and its membrane coverings herniate through a defect in the vertebral column

early surgical repair improves chances of survival

60
Q

what is anencephaly

A

where a good part of the brain is absent and the skull is wide open - affected infants die in a few days

61
Q

what gene is implicated in psychopathology, what does this suggest

A

Netrin 1 receptor (DCC gene)

abnormalities cause neural dysfunction that causes aberrant perceptions (delusions and hallucinations)

62
Q

name two disorders of neuronal proliferation and migration

A

microcephaly
lissencephaly

63
Q

are disorders of neuronal proliferation and migration fatal

A

no - often result in psychomotor deficits and seizures

64
Q

what is lissencephaly

A

a lack of neural folds (brain is smooth)

65
Q

what is microcephaly

A

brain and skull are small in size

332: Neurobiology (15 decks)

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